ANDROID: dma-buf: system_heap: kmap_local_page instead of kmap_atomic

kmap_atomic was deprecated in 5.11, and checkpatch now warns about use
of it. Replace with kmap_local_page, and do not manually disable
preemption or page faults.

Bug: 264474028
Fixes: ef2ab77c ("ANDROID: dma-buf: system_heap: Add pagepool support to system heap")
Change-Id: Idd6413ff56aadf4fd925acb6f567366d0e03166f
Signed-off-by: T.J. Mercier <tjmercier@google.com>