usb: gadget: u_audio: Check return codes from usb_ep_enable and config_ep_by_speed.

usb: gadget: u_audio: Check return codes from usb_ep_enable and config_ep_by_speed.

These functions can fail if descriptors are malformed, or missing,
for the selected USB speed.

Fixes: eb9fecb9e69b ("usb: gadget: f_uac2: split out audio core")
Fixes: 24f779dac8f3 ("usb: gadget: f_uac2/u_audio: add feedback endpoint support")
Cc: stable@vger.kernel.org
Signed-off-by: Chris Wulff <crwulff@gmail.com>
Link: https://lore.kernel.org/r/20240721192314.3532697-2-crwulff@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>