The PS/2 mouse device responds to a reset command with a sequence of
ACK(fa), RESULT(aa) and ID(00). Most PS/2 mice immediately returns
ACK, but spend sometime before sending RESULT. The Armada takes time
before ACK; extra delay is necessary before the call to read ACK.
The problem was reported in comp.unix.bsd.freebsd.misc and the patch
was tested by the reporter. No PR was filed, by the way.