drm/amd/display: Fix OTG H timing reset for dcn314

[Why]
When ODM is enabled, H timing control register reset
to 0. Div mode manual field get overwritten causing
no display on certain modes for dcn314.

[How]
Use REG_UPDATE instead of REG_SET to set div_mode
field.
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Reviewed-by: Nicholas Kazlauskas <Nicholas.Kazlauskas@amd.com>
Acked-by: Brian Chang <Brian.Chang@amd.com>
Signed-off-by: Duncan Ma <duncan.ma@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/dcn314/dcn314_optc.c

@@ -98,7 +98,8 @@ static void optc314_set_odm_combine(struct timing_generator *optc, int *opp_id,
 	REG_UPDATE(OPTC_WIDTH_CONTROL,
 			OPTC_SEGMENT_WIDTH, mpcc_hactive);
 
-	REG_SET(OTG_H_TIMING_CNTL, 0, OTG_H_TIMING_DIV_MODE, opp_cnt - 1);
+	REG_UPDATE(OTG_H_TIMING_CNTL,
+			OTG_H_TIMING_DIV_MODE, opp_cnt - 1);
 	optc1->opp_count = opp_cnt;
 }