drm/amd/display: Refactor to remove diags specific rgam func

[Why]
It has duplicate code for building regamma curve

[How]
Remove the duplicate code and use the same function for building regamma
Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/modules/color/color_gamma.h

@@ -103,10 +103,6 @@ bool mod_color_calculate_regamma_params(struct dc_transfer_func *output_tf,
 bool mod_color_calculate_degamma_params(struct dc_transfer_func *output_tf,
 		const struct dc_gamma *ramp, bool mapUserRamp);
 
-bool mod_color_calculate_curve(enum dc_transfer_func_predefined  trans,
-		struct dc_transfer_func_distributed_points *points,
-		uint32_t sdr_ref_white_level);
-
 bool mod_color_calculate_degamma_curve(enum dc_transfer_func_predefined trans,
 				struct dc_transfer_func_distributed_points *points);