nb/intel/gm45: Allocate a 8M TSEG region

Tested on Thinkpad X200.

Change-Id: I9db7a71608aaec956a7b22649498b97d58f35265
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/23418
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/gm45/gm45.h b/src/northbridge/intel/gm45/gm45.h
index 34f734c..df9c449 100644
--- a/src/northbridge/intel/gm45/gm45.h
+++ b/src/northbridge/intel/gm45/gm45.h
@@ -433,6 +433,7 @@
 
 u32 decode_igd_memory_size(u32 gms);
 u32 decode_igd_gtt_size(u32 gsm);
+u32 decode_tseg_size(u8 esmramc);
 
 void init_iommu(void);