OMAPDSS: VENC: Add error handling for venc_probe_pdata

Add proper error handling for venc_probe_pdata(). This will cause
EPROBE_DEFER to be properly passed upwards, causing the VENC driver to be
probed again later if a resource was missing.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>