acerhdf: remove "chk_off" as it was only needed for T31 netbooks

Remove "chk_off" as it was only needed for T31 netbooks.  But those
netbooks can also be handled just with "cmd_off" register (0x9e) for
reading the state back.

Signed-off-by: Peter Feuerer <peter@piie.net>
Cc: Borislav Petkov <petkovbb@gmail.com>
Cc: Andreas Mohr <andi@lisas.de>
Cc: Len Brown <lenb@kernel.org>
Cc: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>