defconfig: Enable UAC2 and UVC configs for sdmsteppe

Add required configs for enabling usb audio & video class drivers
for sdmsteppe.

Change-Id: If756d23414a1aacc392904b2c0a4e5b0d52045f1
Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>