drm/amd/display: Make core_dcn4_ip_caps_base static

The sparse tool complains as follows:

drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4.c:12:28: warning:
symbol 'core_dcn4_ip_caps_base' was not declared. Should it be static?

This symbol is not used outside of dcn35_hubp.c, so marks it static.

And do not want to change it, so mark it const.

Signed-off-by: Jinjie Ruan <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/dml2/dml21/src/dml2_core/dml2_core_dcn4.c

···
 #include "dml2_debug.h"
 #include "lib_float_math.h"
 
-struct dml2_core_ip_params core_dcn4_ip_caps_base = {
+static const struct dml2_core_ip_params core_dcn4_ip_caps_base = {
 	// Hardcoded values for DCN3x
 	.vblank_nom_default_us = 668,
 	.remote_iommu_outstanding_translations = 256,