drm/amdgpu: make some DP parameters const

Ported from similar radeon patch.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/atombios_dp.c

@@ -203,7 +203,7 @@ void amdgpu_atombios_dp_aux_init(struct amdgpu_connector *amdgpu_connector)
 #define DP_VOLTAGE_MAX         DP_TRAIN_VOLTAGE_SWING_LEVEL_3
 #define DP_PRE_EMPHASIS_MAX    DP_TRAIN_PRE_EMPH_LEVEL_3
 
-static void amdgpu_atombios_dp_get_adjust_train(u8 link_status[DP_LINK_STATUS_SIZE],
+static void amdgpu_atombios_dp_get_adjust_train(const u8 link_status[DP_LINK_STATUS_SIZE],
 						int lane_count,
 						u8 train_set[4])
 {
@@ -265,7 +265,7 @@ static int amdgpu_atombios_dp_get_max_dp_pix_clock(int link_rate,
  * if the max lane# < low rate lane# then use max lane# instead.
  */
 static int amdgpu_atombios_dp_get_dp_lane_number(struct drm_connector *connector,
-					  u8 dpcd[DP_DPCD_SIZE],
+						 const u8 dpcd[DP_DPCD_SIZE],
 						 int pix_clock)
 {
 	int bpp = amdgpu_atombios_dp_convert_bpc_to_bpp(amdgpu_connector_get_monitor_bpc(connector));
@@ -284,7 +284,7 @@ static int amdgpu_atombios_dp_get_dp_lane_number(struct drm_connector *connector
 }
 
 static int amdgpu_atombios_dp_get_dp_link_clock(struct drm_connector *connector,
-					 u8 dpcd[DP_DPCD_SIZE],
+						const u8 dpcd[DP_DPCD_SIZE],
 						int pix_clock)
 {
 	int bpp = amdgpu_atombios_dp_convert_bpc_to_bpp(amdgpu_connector_get_monitor_bpc(connector));