Input: atmel_mxt_ts - parse T6 reports

The normal messages sent after boot or NVRAM update are T6 reports,
containing a status, and the config memory checksum.  Parse them and dump
a useful info message.

This patch tested on an MXT224E.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>