drm/amd/display: fix hdmi_encoded_link_bw definition

Some of the data structures are hidden when CONFIG_DRM_AMD_DC_DCN is
disabled, which leads to a link failure:

drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:234:21: error: 'union hdmi_encoded_link_bw' declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
  234 |         const union hdmi_encoded_link_bw hdmi_encoded_link_bw)
      |                     ^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:234:42: error: parameter 2 ('hdmi_encoded_link_bw') has incomplete type
  234 |         const union hdmi_encoded_link_bw hdmi_encoded_link_bw)
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:232:17: error: function declaration isn't a prototype [-Werror=strict-prototypes]
  232 | static uint32_t intersect_frl_link_bw_support(
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c: In function 'get_active_converter_info':
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:1126:76: error: storage size of 'hdmi_encoded_link_bw' isn't known
 1126 |                                                 union hdmi_encoded_link_bw hdmi_encoded_link_bw;
      |                                                                            ^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/../display/dc/link/link_dp_capability.c:1130:101: error: 'struct <anonymous>' has no member named 'MAX_ENCODED_LINK_BW_SUPPORT'
 1130 |                                                                                 hdmi_color_caps.bits.MAX_ENCODED_LINK_BW_SUPPORT);

There is probably no need to hide the data structure, and removing
the #ifdef makes it build cleanly.

Fixes: d5a43956 ("drm/amd/display: move dp capability related logic to link_dp_capability")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>