watchdog: fix GETTIMEOUT ioctl in booke_wdt

Commit dcfb7484 ([WATCHDOG] fix book E watchdog to take
WDIOC_SETTIMEOUT arg in seconds) fixed SETTIMEOUT ioctl
to use seconds as a parameter instead of some hardware-specific
"period", but missed to apply similar changes to GETTIMEOUT,
so it still returns "period" value. Let's fix it!
Also, while at it, make SETTIMEOUT ioctl return real timeout
value as it should do according to the documentation.

Signed-off-by: Dmitry Artamonow <mad_soft@inbox.ru>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>