usb: gadget: f_uac2: Adds support for S24_LE

Adds support for S24_LE format along with the
existing S24_3LE. The S24_LE and S24_3LE has same
bit resolution but different slot sizes, so added
a new fields p_sres and c_sbres to f_uac2 opts
to help distinguish these two formats. Adds two alt
settings so HOST can select the alt setting to select
S24_LE format.

Change-Id: Id58b76a3e344eaa36db8fce8adde16f0ac052e9f
Signed-off-by: Sriharsha Allenki <sallenki@codeaurora.org>