BACKPORT: drm/virtio: use kvmalloc for large allocations

We observed that some of virtio_gpu_object_shmem_init() allocations
can be rather costly - order 6 - which can be difficult to fulfill
under memory pressure conditions. Switch to kvmalloc_array() in
virtio_gpu_object_shmem_init() and let the kernel vmalloc the entries
array.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
(cherry picked from commit ea86f3defd55f141a44146e66cbf8ffb683d60da)
Bug: 171450517
Test: run clash of clans game on Kled device
Change-Id: I1b585177c7ebfbd95a494fc4e65150cd522517cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2519343


Reviewed-by: Suleiman Souhlal <suleiman@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: David Stevens <stevensd@chromium.org>
Commit-Queue: Sergey Senozhatsky <senozhatsky@chromium.org>
Tested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Alistair Delva <adelva@google.com>