i945: Consolidate FADT code

Change-Id: I076cba7d21926cabf90d485de50268ae40c435f3
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/7087
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

src/Kconfig

@@ -474,6 +474,10 @@ config PER_DEVICE_ACPI_TABLES
 	bool
 	default n
 
+config COMMON_FADT
+	bool
+	default n
+
 #These Options are here to avoid "undefined" warnings.
 #The actual selection and help texts are in the following menu.