drm/amd/display: make some functions static

These functions are not used outside the file dcn32_dccg.c, so the
modification is defined as static.

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn32/dcn32_dccg.c:257:6: warning: no previous prototype for ‘dccg32_otg_drop_pixel’.
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn32/dcn32_dccg.c:248:6: warning: no previous prototype for ‘dccg32_otg_add_pixel’.
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn32/dcn32_dccg.c:211:6: warning: no previous prototype for ‘dccg32_set_dpstreamclk’.
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn32/dcn32_dccg.c:136:6: warning: no previous prototype for ‘dccg32_set_dtbclk_dto’.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2142Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_dccg.c

@@ -133,7 +133,7 @@ static void dccg32_set_dtbclk_p_src(
 }
 
 /* Controls the generation of pixel valid for OTG in (OTG -> HPO case) */
-void dccg32_set_dtbclk_dto(
+static void dccg32_set_dtbclk_dto(
 		struct dccg *dccg,
 		const struct dtbclk_dto_params *params)
 {
@@ -208,7 +208,7 @@ static void dccg32_get_dccg_ref_freq(struct dccg *dccg,
 	return;
 }
 
-void dccg32_set_dpstreamclk(
+static void dccg32_set_dpstreamclk(
 		struct dccg *dccg,
 		enum streamclk_source src,
 		int otg_inst,
@@ -245,7 +245,7 @@ void dccg32_set_dpstreamclk(
 	}
 }
 
-void dccg32_otg_add_pixel(struct dccg *dccg,
+static void dccg32_otg_add_pixel(struct dccg *dccg,
 		uint32_t otg_inst)
 {
 	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);
@@ -254,7 +254,7 @@ void dccg32_otg_add_pixel(struct dccg *dccg,
 			OTG_ADD_PIXEL[otg_inst], 1);
 }
 
-void dccg32_otg_drop_pixel(struct dccg *dccg,
+static void dccg32_otg_drop_pixel(struct dccg *dccg,
 		uint32_t otg_inst)
 {
 	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);