drm/radeon: Use kvmalloc for CS chunks

The number of chunks/chunks_array may be passed in
by userspace and can be large.

It has been observed to cause kcalloc failures from trinity fuzzy test:

 WARNING: CPU: 0 PID: 5487 at mm/page_alloc.c:4385
 __alloc_pages_nodemask+0x2d8/0x14d0

Obviously, the required order in this case is larger than MAX_ORDER.
So, just use kvmalloc instead.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Chen Li <chenli@uniontech.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>