i945: Find memory controller by slot instead of by PCIID.

Slot is the same on all model but PCIID varies. Tested on AOA150.

Change-Id: I474548971ea140f25326a68fe8e86698a6725dea
Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-on: http://review.coreboot.org/7569
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/northbridge/intel/i945/acpi.c

@@ -39,7 +39,7 @@ unsigned long acpi_fill_mcfg(unsigned long current)
 	u32 pciexbar_reg;
 	int max_buses;
 
-	dev = dev_find_device(0x8086, 0x27a0, 0);
+	dev = dev_find_slot(0, PCI_DEVFN(0,0));
 	if (!dev)
 		return current;