drm/amdkfd: fix 32-bit overflow in CWSR total size calculation

drm/amdkfd: fix 32-bit overflow in CWSR total size calculation

total_cwsr_size was computed in 32-bit before being used as a BO/SVM
allocation size.
With large ctx_save_restore_area_size and debug_memory_size
multiplied by the XCC count, the product can wrap,
yielding an undersized CWSR save area that firmware later overruns.

Promote total_cwsr_size to u64 and use check_add_overflow()/
check_mul_overflow() in both kfd_queue_acquire_buffers() and
kfd_queue_release_buffers().

Signed-off-by: Yongqiang Sun <Yongqiang.Sun@amd.com>
Reviewed-by: Philip Yang <philip.yang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>