usb: r8a66597-hcd: fix up error path.

Currently when registration fails we're left with a stray reference to
release_mem_region(), this leads to the following case:

    r8a66597_hcd r8a66597_hcd: irq 13, io base 0x18040000
    drivers/usb/host/r8a66597-hcd.c: register access fail.
    r8a66597_hcd r8a66597_hcd: startup error -6
    r8a66597_hcd r8a66597_hcd: USB bus 1 deregistered
    drivers/usb/host/r8a66597-hcd.c: Failed to add hcd
    Trying to free nonexistent resource <0000000018040000-0000000018040000>

This fixes it up.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>