atkbd: Fix first keystroke force reset

Some i8042 falsely return KBD_ACK for ECHO command which cuase the
keyboard echo test failed.
Without passing echo test, the keyboard is considered as unconfigured.

Though it is an incorrect behavior, we still regard it as a
correct to prevent the force reset (a step for configure a keyboard)
of whole keyboard when the first key interrupt reached.

Co-Authored-By: Aymeric Wibo <obiwac@freebsd.org>
Reviewed By: wulf, obiwac, emaste
Sponsored By: FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D50498