usb: gadget: f_accessory: move userspace interface to uapi

Move the entire contents of linux/usb/f_accessory.h header to uapi,
it only contains a userspace interface.

Change-Id: Ieb5547da449588ae554988a201c0e6b4e3afc531
Signed-off-by: Colin Cross <ccross@android.com>
Git-commit: 7a6a0851afc3c63400f561b876374ca105448d0e
Git-Repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>