drm/amd/display/dc/core/dc_link_ddc: Move DP_DVI_CONVERTER_ID_{4, 5} to where they're used

This patch fixes >200 warnings.

Fixes the following W=1 kernel build warning(s):

 from drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:31:
 drivers/gpu/drm/amd/amdgpu/../display/include/ddc_service_types.h:126:22: warning: ‘DP_DVI_CONVERTER_ID_5’ defined but not used [-Wunused-const-variable=]
 126 | static const uint8_t DP_DVI_CONVERTER_ID_5[] = "3393N2";
 | ^~~~~~~~~~~~~~~~~~~~~
 drivers/gpu/drm/amd/amdgpu/../display/include/ddc_service_types.h:125:22: warning: ‘DP_DVI_CONVERTER_ID_4’ defined but not used [-Wunused-const-variable=]
 125 | static const uint8_t DP_DVI_CONVERTER_ID_4[] = "m2DVIa";
 | ^~~~~~~~~~~~~~~~~~~~~

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>