UPSTREAM: usb: gadget: function: Remove unused declarations

These declarations are not implemented anymore, remove them.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20230818124025.51576-1-yuehaibing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 308685568
Bug: 301887900
(cherry picked from commit ae257611
 https://kernel.googlesource.com/pub/scm/linux/kernel/git/gregkh/usb

 usb-next)
Signed-off-by: Avichal Rakesh <arakesh@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:de5c447459e97aa13b3ee336a9587624cf37af05)
Merged-In: Ib1ac4d7ecada70d467cd9b2d688f13ba3797a05c
Change-Id: Ib1ac4d7ecada70d467cd9b2d688f13ba3797a05c