northbridge/amd/amdmct: Fix burst write depth on K10 rev. D and later

The BKDG for K10 revision D and later processors recommends a smaller
MCT burst write queue depth when using unganged memory.

TEST: Booted ASUS KFSN4-DRE with both Opteron 8356 and Opteron 2431
processors.

Change-Id: I36718d4972c9d2d0bdd3274191503b5fcd803f15
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: http://review.coreboot.org/8500
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
1 file changed