drm/amd/display: remove unnecessary else by CONFIG_DRM_AMD_DC_DCN
[Why & How]
CONFIG_DRM_AMD_DC_DCN is used by pass the compilation failures, but DC
code should be OS-agnostic.
This patch fixes it by removing unnecessasry CONFIG_DRM_AMD_DC_DCN
guards for #if-#else clause.
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com> Acked-by: Stylon Wang <stylon.wang@amd.com> Signed-off-by: Alex Hung <alex.hung@amd.com> Tested-by: Daniel Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>