usb: musb: blackfin: call gpio_free() on error path in musb_platform_init()

Blackfin's musb_platform_init() needs to call gpio_free() for error cleanup iff
otg_get_transceiver() call returns NULL.

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>