Fix day of week in mc146818

Fix day of week in mc146818

According to mc146818 specification, Day of Week register (#6) is between 1
and 7, 1 representing Sunday. According C specification, tm_wday field in
struct tm is between 0 and 6, 0 representing Sunday.

Bit 2 of register B (#11) is named DM (data mode) and specifies if RTC
stores values in BCD or in binary form.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6310 c046a42c-6fe2-441c-8c8c-71466251a162