i2c: qup: skip qup_i2c_suspend if the device is already runtime suspended

i2c: qup: skip qup_i2c_suspend if the device is already runtime suspended

If the i2c device is already runtime suspended, if qup_i2c_suspend is
executed during suspend-to-idle or suspend-to-ram it will result in the
following splat:

WARNING: CPU: 3 PID: 1593 at drivers/clk/clk.c:476 clk_core_unprepare+0x80/0x90
Modules linked in:

CPU: 3 PID: 1593 Comm: bash Tainted: G        W       4.8.0-rc3 #14
Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
PC is at clk_core_unprepare+0x80/0x90
LR is at clk_unprepare+0x28/0x40
pc : [<ffff0000086eecf0>] lr : [<ffff0000086f0c58>] pstate: 60000145
Call trace:
 clk_core_unprepare+0x80/0x90
 qup_i2c_disable_clocks+0x2c/0x68
 qup_i2c_suspend+0x10/0x20
 platform_pm_suspend+0x24/0x68
 ...

This patch fixes the issue by executing qup_i2c_pm_suspend_runtime
conditionally in qup_i2c_suspend.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Andy Gross <andy.gross@linaro.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: stable@kernel.org