soc/amd/common/pi: Correct top of DRAM reporting by AGESA

Accurately reflect the intention of the syslimit value returned
from AmdInitPost().  Assume FFs for the non-present bits.

BUG=b:118178425
TEST=Boot Grunt and verify reported value = TOM2-1.

Change-Id: Ie8ea4fcbfd52c46ad441890f0decaf0f55816cfd
Signed-off-by: Marshall Dawson <marshalldawson3rd@gmail.com>
Reviewed-on: https://review.coreboot.org/29229
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/soc/amd/common/block/pi/agesawrapper.c

@@ -164,7 +164,7 @@ static void print_init_post_settings(AMD_POST_PARAMS *parms)
 		break;
 	}
 
-	syslimit = (u64)parms->MemConfig.SysLimit * 64 * KiB;
+	syslimit = (u64)(parms->MemConfig.SysLimit + 1) * 64 * KiB - 1;
 	bottomio = (u64)parms->MemConfig.BottomIo * 64 * KiB;
 
 	uma_size = (u64)parms->MemConfig.UmaSize * 64 * KiB;