x86 setup: handle more than 8 CPU flag words

Checkin e38e05a85828dac23540cd007df5f20985388afc added a 9th CPU flag
word, but didn't adjust the boot code to match.  This patch adds the
necessary boot code support.

Note: due to a typo in an #if statement, it didn't trigger the #error
this was supposed to do.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>