msm: ipa: use GFP_ATOMIC for DMA memory allocation during SSR

SSR logic is executed during device shutdown. During device
shutdown the Linux tasks (processes) are moving to SIGKILL
state. If a DMA allocation from the kernel happens
in a context of a process in SIGKILL state and page migration
is needed, the allocation will fail.
Use GFP_ATOMIC allocation flag during SSR. This will
utilize the atomic memory pool and will not require page
migration.

CRs-fixed: 1077811
Change-Id: Ie06b85d1f9d0a230c3d3832b6f0bbcdefc520c1e
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>
Signed-off-by: Utkarsh Saxena <usaxena@codeaurora.org>