drm/amdkfd: Fix NULL Pointer Dereference in KFD queue

drm/amdkfd: Fix NULL Pointer Dereference in KFD queue

Through KFD IOCTL Fuzzing we encountered a NULL pointer derefrence
when calling kfd_queue_acquire_buffers.

Fixes: 629568d25fea ("drm/amdkfd: Validate queue cwsr area and eop buffer size")
Signed-off-by: Andrew Martin <Andrew.Martin@amd.com>
Reviewed-by: Philip Yang <Philip.Yang@amd.com>
Signed-off-by: Andrew Martin <Andrew.Martin@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 049e5bf3c8406f87c3d8e1958e0a16804fa1d530)
Cc: stable@vger.kernel.org