UPSTREAM: usb: gadget: f_uac1: allow changing interface name via configfs

This adds "function_name" configfs entry to change string value
of the iInterface field. This field will be shown in Windows' audio
settings panel, so being able to change it is useful. It will default
to "AC Interface" just as before if unchanged.

Signed-off-by: Yunhao Tian <t123yh.xyz@gmail.com>
Link: https://lore.kernel.org/r/20220122112446.1415547-1-t123yh.xyz@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Bug: 235196743
(cherry picked from commit dfb05b5d)
Change-Id: Ibd0e417ab82efe1fb3aa6fd5bb33fb70f113cf1a
Signed-off-by: Luiz Matheus <luizmmat@motorola.com>