drm/amd/display: change several dcn30 variables storage-class-specifier to static

smatch reports these similar problems in dcn30
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn30/dcn30_dwb.c:223:25:
  warning: symbol 'dcn30_dwbc_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn30/dcn30_mmhubbub.c:214:28:
  warning: symbol 'dcn30_mmhubbub_funcs' was not declared. Should it be static?
drivers/gpu/drm/amd/amdgpu/../display/dc/dcn30/dcn30_mpc.c:1402:24:
  warning: symbol 'dcn30_mpc_funcs' was not declared. Should it be static?

All of these are only used in their definition file, so they should be static
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_dwb.c

@@ -220,7 +220,7 @@ void dwb3_set_denorm(struct dwbc *dwbc, struct dc_dwb_params *params)
 }
 
 
-const struct dwbc_funcs dcn30_dwbc_funcs = {
+static const struct dwbc_funcs dcn30_dwbc_funcs = {
 	.get_caps		= dwb3_get_caps,
 	.enable			= dwb3_enable,
 	.disable		= dwb3_disable,

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_mmhubbub.c

@@ -211,7 +211,7 @@ static void mmhubbub3_config_mcif_arb(struct mcif_wb *mcif_wb,
 	REG_UPDATE(MCIF_WB_ARBITRATION_CONTROL, MCIF_WB_CLIENT_ARBITRATION_SLICE,  params->arbitration_slice);
 }
 
-const struct mcif_wb_funcs dcn30_mmhubbub_funcs = {
+static const struct mcif_wb_funcs dcn30_mmhubbub_funcs = {
 	.warmup_mcif		= mmhubbub3_warmup_mcif,
 	.enable_mcif		= mmhubbub2_enable_mcif,
 	.disable_mcif		= mmhubbub2_disable_mcif,

drivers/gpu/drm/amd/display/dc/dcn30/dcn30_mpc.c

@@ -1399,7 +1399,7 @@ static void mpc3_set_mpc_mem_lp_mode(struct mpc *mpc)
 	}
 }
 
-const struct mpc_funcs dcn30_mpc_funcs = {
+static const struct mpc_funcs dcn30_mpc_funcs = {
 	.read_mpcc_state = mpc1_read_mpcc_state,
 	.insert_plane = mpc1_insert_plane,
 	.remove_mpcc = mpc1_remove_mpcc,