usb: gadget: audio: Fix audio compilation
usb: gadget: audio: Fix audio compilation

Prevent audio compilation when sound flag is disabled.

Change-Id: Ifd14665535f0407bfb2b3fe47f3699ee739f5aef
Signed-off-by: Anna Perel <c45864de69324ed72976f0f8987640a392ee613d@codeaurora.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas