usb: gadget: Fix inconsistent indent

Remove whitespace and use tab as indent
Acked-by: NFelipe Balbi <balbi@kernel.org>
Signed-off-by: NWei Ming Chen <jj251510319013@gmail.com>
Link: https://lore.kernel.org/r/20210801055454.53015-1-jj251510319013@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>