ath9k: Fix possible double free of PAPRD skb's

ath9k: Fix possible double free of PAPRD skb's

This patch reverts the following commit
ath9k: remove bfs_paprd_timestamp from struct ath_buf_state

Under high interference/noisy environment conditions where PAPRD frames
fails heavily introduces a possibility of double freeing skb's and causes
kernel panic after some time.This patch reverts back to the original approach
of using paprd_timestamp before freeing the PAPRD frame skb's

[  194.193705] Pid: 0, comm: swapper Tainted: G      D WC
2.6.35-22-generic #33-Ubuntu
[  194.193712] Call Trace:
[  194.193722]  [<c05c6468>] ? printk+0x2d/0x35
[  194.193732]  [<c05c63c3>] panic+0x5a/0xd2
[  194.193741]  [<c05ca3ed>] oops_end+0xcd/0xd0
[  194.193750]  [<c0105f74>] die+0x54/0x80
[  194.193758]  [<c05c9a16>] do_trap+0x96/0xc0
[  194.193837]  [<c0103fb0>] ? do_invalid_op+0x0/0xa0
[  194.193846]  [<c010403b>] do_invalid_op+0x8b/0xa0
[  194.193856]  [<c020bd4c>] ? kfree+0xec/0xf0
[  194.193866]  [<c012ce18>] ? default_spin_lock_flags+0x8/0x10
[  194.193877]  [<c01de47a>] ? free_one_page+0x12a/0x2d0
[  194.193888]  [<c01e04dc>] ? __free_pages+0x1c/0x40
[  194.193897]  [<c05c97a7>] error_code+0x73/0x78
[  194.193906]  [<c020bd4c>] ? kfree+0xec/0xf0
[  194.193915]  [<c04ecdd0>] ? skb_release_data+0x70/0xa0
[  194.193924]  [<c04ecdd0>] skb_release_data+0x70/0xa0
[  194.193933]  [<c04ec997>] __kfree_skb+0x17/0x90
[  194.193941]  [<c04eca31>] consume_skb+0x21/0x40
[  194.193964]  [<f85e0b70>] ieee80211_tx_status+0x760/0x860 [mac80211]
[  194.193979]  [<f85caddf>] ath_tx_complete_buf+0x1bf/0x2c0 [ath9k]
[  194.193988]  [<c05c8b9f>] ? _raw_spin_lock_irqsave+0x2f/0x50
[  194.193997]  [<c04ec40e>] ? skb_queue_tail+0x3e/0x50
[  194.194010]  [<f85cc803>] ath_tx_complete_aggr+0x823/0x940 [ath9k]
[  194.194021]  [<c0108a28>] ? sched_clock+0x8/0x10
[  194.194030]  [<c016bf14>] ? sched_clock_local+0xa4/0x180
[  194.194040]  [<c0139f57>] ? enqueue_sleeper+0x1e7/0x2b0
[  194.194051]  [<c013a194>] ? enqueue_entity+0x174/0x200
[  194.194064]  [<f85ce83d>] ath_tx_edma_tasklet+0x2bd/0x3b0 [ath9k]
[  194.194074]  [<c05c8b9f>] ? _raw_spin_lock_irqsave+0x2f/0x50
[  194.194088]  [<f85c7b9f>] ath9k_tasklet+0x9f/0x190 [ath9k]
[  194.194097]  [<c01505d7>] tasklet_action+0xa7/0xb0
[  194.194107]  [<c015127c>] __do_softirq+0x9c/0x1b0
[  194.194117]  [<c01a7f64>] ? irq_to_desc+0x14/0x20
[  194.194126]  [<c0124fc4>] ? ack_apic_level+0x64/0x1f0
[  194.194136]  [<c01513d5>] do_softirq+0x45/0x50
[  194.194145]  [<c0151545>] irq_exit+0x65/0x70
[  194.194153]  [<c05cf665>] do_IRQ+0x55/0xc0
[  194.194162]  [<c016a6c7>] ? hrtimer_start+0x27/0x30
[  194.194171]  [<c0103630>] common_interrupt+0x30/0x38
[  194.194181]  [<c012c21a>] ? native_safe_halt+0xa/0x10
[  194.194268]  [<c010a2f9>] default_idle+0x49/0xb0
[  194.194277]  [<c0101fcc>] cpu_idle+0x8c/0xd0
[  194.194286]  [<c05b2431>] rest_init+0x71/0x80
[  194.194295]  [<c081981a>] start_kernel+0x36e/0x374
[  194.194305]  [<c08199dd>] ? pass_all_bootoptions+0x0/0xa
[  194.194314]  [<c08190d7>] i386_start_kernel+0xd7/0xdf
[  194.194364] panic occurred, switching back to text console

Signed-off-by: Mohammed Shafi Shajakhan <mshajakhan@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>