drm/amd/display: Make dcn35_hubp_funcs static

The sparse tool complains as follows:

drivers/gpu/drm/amd/amdgpu/../display/dc/hubp/dcn35/dcn35_hubp.c:191:19: warning:
	symbol 'dcn35_hubp_funcs' was not declared. Should it be static?

This symbol is not used outside of dcn35_hubp.c, so marks it static.
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/hubp/dcn35/dcn35_hubp.c

@@ -188,7 +188,7 @@ void hubp35_program_surface_config(
 	hubp35_program_pixel_format(hubp, format);
 }
 
-struct hubp_funcs dcn35_hubp_funcs = {
+static struct hubp_funcs dcn35_hubp_funcs = {
 	.hubp_enable_tripleBuffer = hubp2_enable_triplebuffer,
 	.hubp_is_triplebuffer_enabled = hubp2_is_triplebuffer_enabled,
 	.hubp_program_surface_flip_and_addr = hubp3_program_surface_flip_and_addr,