usb: gadget: f_uac2: fix endianness of 'struct cntrl_*_lay3'

usb: gadget: f_uac2: fix endianness of 'struct cntrl_*_lay3'

The list [1] of commits doing endianness fixes in USB subsystem is long
due to below quote from USB spec Revision 2.0 from April 27, 2000:

------------
8.1 Byte/Bit Ordering

Multiple byte fields in standard descriptors, requests, and responses
are interpreted as and moved over the bus in little-endian order, i.e.
LSB to MSB.
------------

This commit belongs to the same family.

[1] Example of endianness fixes in USB subsystem:
commit b692fb1bfd40 ("usb: gadget: f_uac2: endianness fixes.")
commit 9693b0c265ea ("usb: gadget: f_uac1: endianness fixes.")
commit d292e1dfeeff ("USB: chaoskey: fix Alea quirk on big-endian hosts")
commit 44f7b4b02db3 ("usb: gadget: acm: fix endianness in notifications")
commit ffbdff626e53 ("ACM gadget: fix endianness in notifications")
commit e7cce808e1df ("cdc-wdm: fix endianness bug in debug statements")
commit ff9a9876ef31 ("usb: gadget: uvc: Fix endianness mismatches")
       list goes on

Fixes: 6049421176fb ("usb: gadget: Add Audio Class 2.0 Driver")
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>