pxafb_init_fbinfo() can not only report errors caused by failed
allocations but also when the clock can't be found.

To fix this, return an error pointer instead of NULL in case of errors,
and up-chain the result.
Signed-off-by: NDaniel Mack <daniel@zonque.org>
Reviewed-by: NRobert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: NBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>