Fixed broken MTRR for >4GB memory on AMD K8 fam 0fh rev <=E

Fixed broken MTRR for >4GB memory on AMD K8 fam 0fh rev <=E

AMD K8 rev F and later implements a bit SYSCFG_MSR_TOM2WB to
mark dram memory above 4GB as WB. However, AMD K8
rev E and earlier don't implement this bit and therefore need
MTRR spanning dram memory above 4GB. The current implementation
of amd_setup_mtrrs never generate MTRR above 4GB.
This caused memory > 4GB not to be recognized in e.g. Linux on those
rev E or older platforms. This commit should fix that bug.

Signed-off-by: Oskar Enoksson <enok@lysator.liu.se>
Change-Id: Ie568a52a8eb355969c86964d5afc4692e60f69c1
Reviewed-on: http://review.coreboot.org/238
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marcj303@gmail.com>