x86: apic - unify APIC_DIVISOR

Use APIC_DIVISOR being set to 16 for both 32/64bit
mode. To escape APIC timer underflow during calibration
set it to the maximum possible value.

Also typo error (CONFG instead of proper CONFIG) fixed.
The error was caught by Venkatesh Pallipadi, thanks a lot Venkatesh!

See details on http://lkml.org/lkml/2008/10/9/425

Reported-by: Venkatesh Pallipad <venkatesh.pallipadi@intel.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Acked-by: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>