amd/amdgpu: use kmalloc_array to replace kmalloc with multiply

Fix check_patch.pl warning:
WARNING: Prefer kmalloc_array over kmalloc with multiply
+bps = kmalloc(align_space * sizeof((*data)->bps), GFP_KERNEL);
WARNING: Prefer kmalloc_array over kmalloc with multiply
+bps_bo = kmalloc(align_space * sizeof((*data)->bps_bo),
GFP_KERNEL);
kmalloc_array has multiply overflow check, which will be safer.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Bernard Zhao <bernard@vivo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>