drm/amd/display: Fix blend LUT programming

[Why]
LUT write index does not get reset to zero when writing the LUT values
for each separate RGB component, which results in wrong data for 2 of
the 3 components.

[How]
Reset LUT write index to zero before writing each component's data.
Reviewed-by: Krunoslav Kovac <krunoslav.kovac@amd.com>
Acked-by: Hersen Wu <hersenxs.wu@amd.com>
Signed-off-by: Ilya Bakoulin <ilya.bakoulin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_dpp.c

@@ -613,16 +613,19 @@ static void dpp3_program_blnd_pwl(
 			REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, rgb[i].red_reg);
 		REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, last_base_value_red);
 	} else {
+		REG_SET(CM_BLNDGAM_LUT_INDEX, 0, CM_BLNDGAM_LUT_INDEX, 0);
 		REG_UPDATE(CM_BLNDGAM_LUT_CONTROL, CM_BLNDGAM_LUT_WRITE_COLOR_MASK, 4);
 		for (i = 0 ; i < num; i++)
 			REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, rgb[i].red_reg);
 		REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, last_base_value_red);
 
+		REG_SET(CM_BLNDGAM_LUT_INDEX, 0, CM_BLNDGAM_LUT_INDEX, 0);
 		REG_UPDATE(CM_BLNDGAM_LUT_CONTROL, CM_BLNDGAM_LUT_WRITE_COLOR_MASK, 2);
 		for (i = 0 ; i < num; i++)
 			REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, rgb[i].green_reg);
 		REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, last_base_value_green);
 
+		REG_SET(CM_BLNDGAM_LUT_INDEX, 0, CM_BLNDGAM_LUT_INDEX, 0);
 		REG_UPDATE(CM_BLNDGAM_LUT_CONTROL, CM_BLNDGAM_LUT_WRITE_COLOR_MASK, 1);
 		for (i = 0 ; i < num; i++)
 			REG_SET(CM_BLNDGAM_LUT_DATA, 0, CM_BLNDGAM_LUT_DATA, rgb[i].blue_reg);

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_mpc.c

@@ -237,16 +237,19 @@ void mpc32_program_post1dlut_pwl(
 			REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, rgb[i].red_reg);
 		REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, last_base_value_red);
 	} else {
+		REG_SET(MPCC_MCM_1DLUT_LUT_INDEX[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_INDEX, 0);
 		REG_UPDATE(MPCC_MCM_1DLUT_LUT_CONTROL[mpcc_id], MPCC_MCM_1DLUT_LUT_WRITE_COLOR_MASK, 4);
 		for (i = 0 ; i < num; i++)
 			REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, rgb[i].red_reg);
 		REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, last_base_value_red);
 
+		REG_SET(MPCC_MCM_1DLUT_LUT_INDEX[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_INDEX, 0);
 		REG_UPDATE(MPCC_MCM_1DLUT_LUT_CONTROL[mpcc_id], MPCC_MCM_1DLUT_LUT_WRITE_COLOR_MASK, 2);
 		for (i = 0 ; i < num; i++)
 			REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, rgb[i].green_reg);
 		REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, last_base_value_green);
 
+		REG_SET(MPCC_MCM_1DLUT_LUT_INDEX[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_INDEX, 0);
 		REG_UPDATE(MPCC_MCM_1DLUT_LUT_CONTROL[mpcc_id], MPCC_MCM_1DLUT_LUT_WRITE_COLOR_MASK, 1);
 		for (i = 0 ; i < num; i++)
 			REG_SET(MPCC_MCM_1DLUT_LUT_DATA[mpcc_id], 0, MPCC_MCM_1DLUT_LUT_DATA, rgb[i].blue_reg);