Revert "drm/amd/display: Hardware cursor changes color when switched to software cursor"

This reverts commit 272e6aa.

Applying degamma curve to the cursor by default breaks Linux userspace
expectation.

On Linux, AMD display manager enables cursor degamma ROM just for
implict sRGB on HW versions where degamma is split into two blocks:
degamma ROM for pre-defined TFs and `gamma correction` for user/custom
curves, and degamma ROM settings doesn't apply to cursor plane.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1513
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2803
Reported-by: Michel Dänzer <michel.daenzer@mailbox.org>
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4144
Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f6a305d)
Cc: stable@vger.kernel.org

Author: melissawen

drivers/gpu/drm/amd/display/dc/dpp/dcn401/dcn401_dpp_cm.c

@@ -120,10 +120,11 @@ void dpp401_set_cursor_attributes(
 	enum dc_cursor_color_format color_format = cursor_attributes->color_format;
 	int cur_rom_en = 0;
 
-	// DCN4 should always do Cursor degamma for Cursor Color modes
 	if (color_format == CURSOR_MODE_COLOR_PRE_MULTIPLIED_ALPHA ||
 		color_format == CURSOR_MODE_COLOR_UN_PRE_MULTIPLIED_ALPHA) {
-		cur_rom_en = 1;
+		if (cursor_attributes->attribute_flags.bits.ENABLE_CURSOR_DEGAMMA) {
+			cur_rom_en = 1;
+		}
 	}
 
 	REG_UPDATE_3(CURSOR0_CONTROL,