drm/amdkfd: Use kvfree in destroy_crat_image

Now that we use kvmalloc for the crat_image, we need to use kvfree when
we destroy this.

Fixes: d0e63b34 ("drm/amdkfd: Use kvmalloc instead of kmalloc for VCRAT")
Reported-by: Morris Zhang <shiwu.zhang@amd.clm>
Signed-off-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>