drm/radeon/kms: evergreen & ni reset SPI block on CP resume

For some reason SPI block is in broken state after module
unloading. This lead to broken rendering after reloading
module. Fix this by reseting SPI block in CP resume function

Signed-off-by: Jerome Glisse <jglisse@redhat.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>