ABI: configfs-usb-gadget-uac2: fix a broken table

ABI: configfs-usb-gadget-uac2: fix a broken table

Changeset af6cbe09920 ("usb: gadget: f_uac2: add volume and mute support")
added some new elements to the table but didn't care enough to actually
adjust the columns, causing the output to be broken as warned by
Sphinx when producing the documentation.

Readjust it for it to be a valid ReST table.

Fixes: eaf6cbe09920 ("usb: gadget: f_uac2: add volume and mute support")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/d253819a4c201b942d754682bb91dd278300fb79.1632740376.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>