USB HID: move usbhid code from drivers/usb/input to drivers/hid/usbhid

Separate usbhid code into dedicated drivers/hid/usbhid directory as
discussed previously with Greg, so that it eases maintaineance process.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>