USB: fsl_qe_udc: Fix oops on QE UDC probe failure

In case of probing errors the driver kfrees the udc_controller, but it
doesn't set the pointer to NULL.

When usb_gadget_register_driver is called, it checks for udc_controller
!= NULL, the check passes and the driver accesses nonexistent memory.
Fix this by setting udc_controller to NULL in case of errors.

While at it, also implement irq_of_parse_and_map()'s failure and cleanup
cases.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>