drm/amd/display: Drop unused DCN_BASE variable in dcn314_resource.c

Fixes the following W=1 kernel build warning:

drivers/gpu/drm/amd/amdgpu/../display/dc/dcn314/dcn314_resource.c:128:29: warning: ‘DCN_BASE’ defined but not used [-Wunused-const-variable=]
  128 | static const struct IP_BASE DCN_BASE = { { { { 0x00000012, 0x000000C0, 0x000034C0, 0x00009000, 0x02403C00, 0, 0, 0 } },
      |                             ^~~~~~~~

Suggested-by: Roman Li <Roman.Li@amd.com>
Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>