usb: host: xhci-plat: propagate return value of platform_get_irq()

platform_get_irq() returns an error code, but the xhci-plat driver
ignores it and always returns -ENODEV. This is not correct, and
prevents -EPROBE_DEFER from being propagated properly.

CC: <stable@vger.kernel.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>