drm/amdgpu/display: make some functions static

Fixes "no previous prototype" warnings.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/clk_mgr/dcn32/dcn32_clk_mgr.c

@@ -487,7 +487,7 @@ static void dcn32_update_clocks(struct clk_mgr *clk_mgr_base,
 				clk_mgr_base->clks.dispclk_khz / 1000 / 7);
 }
 
-void dcn32_clock_read_ss_info(struct clk_mgr_internal *clk_mgr)
+static void dcn32_clock_read_ss_info(struct clk_mgr_internal *clk_mgr)
 {
 	struct dc_bios *bp = clk_mgr->base.ctx->dc_bios;
 	int ss_info_num = bp->funcs->get_ss_entry_number(

drivers/gpu/drm/amd/display/dc/dcn31/dcn31_dccg.c

@@ -662,7 +662,7 @@ void dccg31_init(struct dccg *dccg)
 	}
 }
 
-void dccg31_otg_add_pixel(struct dccg *dccg,
+static void dccg31_otg_add_pixel(struct dccg *dccg,
 				 uint32_t otg_inst)
 {
 	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);
@@ -671,7 +671,7 @@ void dccg31_otg_add_pixel(struct dccg *dccg,
 			OTG_ADD_PIXEL[otg_inst], 1);
 }
 
-void dccg31_otg_drop_pixel(struct dccg *dccg,
+static void dccg31_otg_drop_pixel(struct dccg *dccg,
 				  uint32_t otg_inst)
 {
 	struct dcn_dccg *dccg_dcn = TO_DCN_DCCG(dccg);

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

@@ -177,7 +177,7 @@ void dccg32_set_dtbclk_dto(
 	}
 }
 
-void dccg32_set_valid_pixel_rate(
+static void dccg32_set_valid_pixel_rate(
 		struct dccg *dccg,
 		int ref_dtbclk_khz,
 		int otg_inst,