adbd: Support for new f_fs descriptor format

The patch "[RFC] usb: gadget: f_fs: Add flags
to  descriptors block" marks the current
usb_functionfs_descs_head format deprecated
and introduces support for sending SuperSpeed
descriptors.

This CL makes adbd to send Descriptors in the
new format. Adbd would fall back to the old
format, if kernel is not able to recognize
the new format. This is done to prevent
adbd from breaking in the older versions
of the kernel.

Bug: 17394972
Change-Id: I1acf684ef8a4dcc612ac20b5abe1e27b43901031
Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>