usb: phy: ab8500: silence some uninitialized variable warnings

Smatch complains that "reg" can be uninitialized if the
abx500_get_register_interruptible() call fails.  It's an interruptable
function, so we should check if the user presses CTRL-C.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>