USB: core: remove set but not used variable 'udev'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/usb/core/driver.c: In function 'usb_driver_claim_interface':
drivers/usb/core/driver.c:513:21: warning:
 variable 'udev' set but not used [-Wunused-but-set-variable]

Since commit c183813f ("USB: remove LPM management from
usb_driver_claim_interface()"), 'udev' is not used.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>