RENOIR loads dmub fw not dmcu, check dmcu only will prevent loading iram,
it breaks backlight control.
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=208277 Acked-by: Alex Deucher <alexander.deucher@amd.com> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com> Signed-off-by: Aaron Ma <aaron.ma@canonical.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: stable@vger.kernel.org