loopback_test: Remove uneeded extern errno
loopback_test: Remove uneeded extern errno

Not only this is superfluous, but it also breaks the Android build.

Signed-off-by: Dimitar Dimitrov <1883968a440f5e821358b2f74d919cb48c4fec38@mm-sol.com>
Reviewed-by: Bryan O'Donoghue <165dc05575478af93ac2f97f67be6e1756010094@linaro.org>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@google.com>

projectara/gbsim,gregkh/gbsim,gregkh/gbsim,projectara/gbsim