Bluetooth: Audio: Shell: Fix ad data returning -1

Several advertising data function could return -1 in case of
errors, which could mess up the advertising data since they are
intended to increment a counter.

Instead of returning an error we use bt_shell_error to inform
the user and then just return with no data changes, so that if
any of them fails, the failing data is just omitted rather
than causing major issues.

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