The size of platform memory above 1M is measured in kilobytes.
This patch fixes truncation of this value. Actually 0 Mb memory size was set by reason of overflow of 16 bit word caused by wrong value used.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Mike Maslenkin <mihailm@parallels.com>
Reviewed-by: Elvin Li <elvin.li@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15318 6f19259b-4bc3-4df7-8a09-765794883524