drm/amd/display: Fix incorrect backlight register offset for DCN

[Why]
Typo in backlight refactor inctroduced wrong register offset.

[How]
Change DCE to DCN register map for PWRSEQ_REF_DIV

Cc: stable@vger.kernel.org
Signed-off-by: Aric Cyr <aric.cyr@amd.com>
Reviewed-by: Ashley Thomas <Ashley.Thomas2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.h

@@ -49,7 +49,7 @@
 #define DCN_PANEL_CNTL_REG_LIST()\
 	DCN_PANEL_CNTL_SR(PWRSEQ_CNTL, LVTMA), \
 	DCN_PANEL_CNTL_SR(PWRSEQ_STATE, LVTMA), \
-	DCE_PANEL_CNTL_SR(PWRSEQ_REF_DIV, LVTMA), \
+	DCN_PANEL_CNTL_SR(PWRSEQ_REF_DIV, LVTMA), \
 	SR(BL_PWM_CNTL), \
 	SR(BL_PWM_CNTL2), \
 	SR(BL_PWM_PERIOD_CNTL), \