drm_hwcomposer: Remove unnecessary warning
When mirroring, this message spams the logs since we loop over the device planes for multiple CRTCs and print this message for the primary planes of each active CRTC.
The case this is avoiding (avoid sharing primary planes) is still valid, afaict, so leave the return statement.
Change-Id: I14afce4918baa5652ec16a3610fe374cccf72422 Signed-off-by: Sean Paul seanpaul@chromium.org