staging: rtl8712: prevent buffer overrun in recvbuf2recvframe

staging: rtl8712: prevent buffer overrun in recvbuf2recvframe

With an RTL8191SU USB adaptor, sometimes the hints for a fragmented
packet are set, but the packet length is too large. Allocate enough
space to prevent memory corruption and a resulting kernel panic [1].

[1] http://www.spinics.net/lists/linux-wireless/msg136546.html

Cc: <stable@vger.kernel.org>
Signed-off-by: Haggai Eran <haggai.eran@gmail.com>
ACKed-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>