ivybridge: Don't propose to include systemagent on native boards.

Change-Id: Ib70a6741b55609840b6fd2fca16bcf9883bf143c
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/6566
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Tested-by: build bot (Jenkins)

src/northbridge/intel/sandybridge/Kconfig

@@ -79,6 +79,7 @@ config DCACHE_RAM_MRC_VAR_SIZE
 
 config HAVE_MRC
 	bool "Add a System Agent binary"
+	depends on !NORTHBRIDGE_INTEL_IVYBRIDGE_NATIVE
 	help
 	  Select this option to add a System Agent binary to
 	  the resulting coreboot image.