OMAPDSS: HDMI: hot plug detect fix

The "OMAPDSS: HDMI: PHY burnout fix" commit switched the HDMI driver
over to using a GPIO for plug detect.  Unfortunately the ->detect()
method was not also updated, causing HDMI to no longer work for the
omapdrm driver (because it would actually check if a connection was
detected before attempting to enable display).

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