Move get_resolution() from omap_dss_device to omap_dss_driver.

This is part of a larger patch-set, which moves the control from omapdss
driver to the display driver.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

If enabling a dss device failed, omapfb didn't exit, leading to crash.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

If there was a dss device without a driver and thus omapfb probe failed,
ref counts could be left to dss devices.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

If the panel's probe had failed, omapfb would still go on, eventually
crashing.

A better fix would be to handle each display properly, and leaving just
the failed display out. But that is a bigger change.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>

Fixes bug causing VRFB memory area to be released twice.
Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>
Reported-by: NEino-Ville Talvala <talvala@stanford.edu>

Signed-off-by: NTomi Valkeinen <tomi.valkeinen@nokia.com>