iichid: The IICHID spec defines the response to the RESET command as two bytes of zeros.

Our recent changes to iichid.c has caused us to attempt to read a
full REPORT instead, and at least one keyboard hangs solid when we
do that.

This patch changes us to be spec-compliant.

Differential Revision: https://reviews.freebsd.org/D53803
MFC after: 1 day
Approved by: re(ccperciva)