usb: gadget: f_uac1: Expose all string descriptors through configfs.

This makes all string descriptors configurable for the UAC1 gadget
so the user can configure names of terminals/controls/alt modes.

Signed-off-by: Chris Wulff <chris.wulff@biamp.com>
Link: https://lore.kernel.org/r/CO1PR17MB541911B0C80D21E4B575E48CE1112@CO1PR17MB5419.namprd17.prod.outlook.com


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