CHROMIUM: Input: atmel_mxt_ts - do not read extra (checksum) byte

CHROMIUM: Input: atmel_mxt_ts - do not read extra (checksum) byte

It isn't sent, nor checked anyway, so don't bother reading it.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
BUG=chromium-os:27713
TEST=builds clean; atmel_mxt_ts driver probes device properly and handles
  contact data.
  Use #define DEBUG build to confirm only 8 bytes are read per message.
   (not 9 as before).

Change-Id: I03bac9c81d3fb6f5411ff42b2a16892d5ba2c44c
Reviewed-on: https://gerrit.chromium.org/gerrit/17947
Commit-Ready: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
Tested-by: Daniel Kurtz <djkurtz@chromium.org>