ASoC: intel: bxt_rt298: Replace GFP_ATOMIC with GFP_KERNEL in broxton_audio_probe

broxton_audio_probe() is never called in atomic context.
This function is only set as ".probe" in "struct platform_driver".

Despite never getting called from atomic context,
broxton_audio_probe() calls devm_kzalloc() with GFP_ATOMIC,
which waits busily for allocation.
GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL,
to avoid busy waiting and improve the possibility of sucessful allocation.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>