drm/virtio: use kvmalloc for large allocations

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>
Link: http://patchwork.freedesktop.org/patch/msgid/20201105014744.1662226-1-senozhatsky@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>