Intel northbridge I945: Apply un-written naming rules

Use NORTHBRIDGE_INTEL_I945 to select the driver directory for build.

Use _SUBTYPE_945GC and _SUBTYPE_945GM to define at compile-time
which model of I945 the driver is built for.

Change-Id: I11b1e0998d0fc28f8946bad4f0989036a9b18af4
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/684
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
diff --git a/src/northbridge/intel/i945/Kconfig b/src/northbridge/intel/i945/Kconfig
index 42cc7ce..093411f 100644
--- a/src/northbridge/intel/i945/Kconfig
+++ b/src/northbridge/intel/i945/Kconfig
@@ -17,15 +17,19 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 ##
 
-config NORTHBRIDGE_INTEL_I945GC
+config NORTHBRIDGE_INTEL_I945
 	bool
+
+if NORTHBRIDGE_INTEL_I945
+
+config NORTHBRIDGE_SPECIFIC_OPTIONS # dummy
+	def_bool y
 	select HAVE_DEBUG_RAM_SETUP
 
-config NORTHBRIDGE_INTEL_I945GM
-	bool
-	select HAVE_DEBUG_RAM_SETUP
-
-if NORTHBRIDGE_INTEL_I945GC || NORTHBRIDGE_INTEL_I945GM
+config NORTHBRIDGE_INTEL_SUBTYPE_I945GC
+	def_bool n
+config NORTHBRIDGE_INTEL_SUBTYPE_I945GM
+	def_bool n
 
 config VGA_BIOS_ID
 	string