USB: gadget: legacy: remove left-over __ref annotations

USB: gadget: legacy: remove left-over __ref annotations

These were added in commit 7ee605c265 ("usb: gadget: add '__ref' for
rndis_config_register() and cdc_config_register()") to silence
modpost, but they didn't fix the real problem - that was fixed later
by removing wrong __init annotations in commit 6bc29c936744 ("usb:
gadget: remove incorrect __init/__exit annotations").

It really never makes sense for a function to be marked __ref unless
it (1) has some conditional that chooses whether to call an __init
function (or access __initdata) or not and (2) has a comment
explaining why the __ref is there and why it is safe.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20210323081607.405904-1-linux@rasmusvillemoes.dk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>