watchdog: it87_wdt: Add support for watchdogs with 8b timers

This patch adds support for watchdogs with 8b timers, like ones in
IT8702F and older revisions of IT8712F Super IO chip, to it87_wdt
driver. This patch should be used after the patch
'it87_wdt: Add support for IT8720F watchdog'.

Signed-off-by: Ondrej Zajicek <santiago@crfreenet.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>