USB: remove match_device

usb_find_device was the only one user of match_device, now
it is removed, so remove match_device to fix the compile warning
below reported by Stephen Rothwell:

	drivers/usb/core/usb.c:596: warning: 'match_device'
	defined but not used

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>