USB: docs: fixed table margin in configfs-usb-gadget-mass-storage

USB: docs: fixed table margin in configfs-usb-gadget-mass-storage

After merging forced_eject patch, there was a broken margin
in the configfs parameters table in the ABI documentation.
This patch fixes it.

Fixes: 421c8d9a20da ("usb: gadget: f_mass_storage: forced_eject attribute")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Maxim Devaev <mdevaev@gmail.com>
Link: https://lore.kernel.org/r/20220723101432.72178-1-mdevaev@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>