drm/amd/display: make dcn32_mmhubbub_funcs static

The symbol is not used outside of the file, so mark it static.

Fixes the following warning:

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn32/dcn32_mmhubbub.c:214:28:
warning: symbol 'dcn32_mmhubbub_funcs' was
not declared. Should it be static?
Reviewed-by: NHarry Wentland <harry.wentland@amd.com>
Signed-off-by: Nruanjinjie <ruanjinjie@huawei.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dcn32/dcn32_mmhubbub.c

@@ -211,7 +211,7 @@ static void mmhubbub32_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 dcn32_mmhubbub_funcs = {
+static const struct mcif_wb_funcs dcn32_mmhubbub_funcs = {
 	.warmup_mcif		= mmhubbub32_warmup_mcif,
 	.enable_mcif		= mmhubbub2_enable_mcif,
 	.disable_mcif		= mmhubbub2_disable_mcif,