Fix memory size reporting on AMD family 14h systems for >= 4GB

Fix memory size reporting on AMD family 14h systems for >= 4GB

Applying Scott Duplichan's fix for memory >=4GB

Adjusted it to the new directory structure (agesa_wrapper was renamed to
just agesa).

Boot-tested and confirmed to work, on my board Linux can now access the
whole RAM.

Change-Id: I31d66a488a7811d214d84653860b3e0116f67d19
Signed-off-by: Scott Duplichan <scott@notabs.org>
Acked-by: Marshall Buschman <mbuschman@lucidmachines.com>
Signed-off-by: Cristian Măgherușan-Stanciu <cristi.magherusan@gmail.com>
Reviewed-on: http://review.coreboot.org/48
Tested-by: build bot (Jenkins)
Reviewed-by: Peter Stuge <peter@stuge.se>