Bluetooth: BAP: Shell: Add missing err check for bt_bap_ep_get_info

Two places we did not have an error check from calling
bt_bap_ep_get_info before accessing the result. These
have simply been added (without an else), as they are
(very) unlikely to fail.

This was caught by coverity and thus fixes those
coverity issues.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>