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

In the Linux kernel, the following vulnerability has been resolved: 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(). (cherry picked from commit 319f7e13423ae3f486b9aea82f9ad2d6af0ee608)