drm/amd/display: fix the build when DRM_AMD_DC_DCN is not set

drm/amd/display: fix the build when DRM_AMD_DC_DCN is not set

commit 5ca9b33ece9aa048b6ec9411f054e1b781662327 upstream

Move the new callback outside of the guard.

Fixes: dc55b106ad47 ("drm/amd/display: Disable phantom OTG after enable for plane disable")
CC: Alvin Lee <Alvin.Lee2@amd.com>
CC: Alan Liu <HaoPing.Liu@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>