ANDROID: usb: gadget: f_accessory: update to usb_gstrings_attach

For AOA re-connection, since the string ID of accessory has been changed
into a non-zero value, the f_accessory failes to call `usb_string_id` to
increment `next_string_id`. This makes the ADB interface display a wrong
name.

Bug: 270044830
Test: CTS Verifier: USB Accessory Test
Test: manual test
Signed-off-by: Kuen-Han Tsai <khtsai@google.com>
Change-Id: I807164588e80b28065e8715591a100392b04d3de