gpu: ion: ion_system_heap: Change allocations to GFP_HIGHUSER

Previously the ion_system_heap was using GFP_KERNEL, forcing all allocations
to be in lowmem.  This quickly causes us to run out of lowmem.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc drivers/staging/android/ion/ion_system_heap.c
Simple merge