drm/radeon: program auxch directly (v2)

The atombios tables have an unfortunate restriction on only
being able to write 12 bytes, MST really wants 16-bytes here,
and since the hw can do it, we should just write directly to it.

This uses a module option to allow for it now, and maybe
we should provide the old code as a fallback for a while.

v2: (agd5f)
- move registers to a proper register header
- only enable on DCE5+
- enable by default on DCE5+
- Switch pad to aux mode before using it
- reformat instance handling to better match the
  rest of the driver

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_mode.h b/drivers/gpu/drm/radeon/radeon_mode.h
index 664825c..60043bf 100644
--- a/drivers/gpu/drm/radeon/radeon_mode.h
+++ b/drivers/gpu/drm/radeon/radeon_mode.h
@@ -722,6 +722,9 @@
 extern void radeon_dp_set_rx_power_state(struct drm_connector *connector,
 					 u8 power_state);
 extern void radeon_dp_aux_init(struct radeon_connector *radeon_connector);
+extern ssize_t
+radeon_dp_aux_transfer_native(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg);
+
 extern void atombios_dig_encoder_setup(struct drm_encoder *encoder, int action, int panel_mode);
 extern void radeon_atom_encoder_init(struct radeon_device *rdev);
 extern void radeon_atom_disp_eng_pll_init(struct radeon_device *rdev);