drm: dp helper: extract drm_dp_clock_recovery_ok

radeon and intel use the exact same definition.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Dave Airlie <airlied@gmail.com>

v2: Kill 2 more helpers in intel_dp.c that I've missed.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>