nb/intel/i945/early_init.c: Add DDR2-667 detection for 945GC

945G-M4 returns : "unknown max. RAM clock (2)",
however, it supports up to DDR2-667MHz.
i945/raminit.c sdram_capabilities_max_supported_memory_frequency()
function returns 667 for case 2.

Change-Id: I3d54c88af897a71db757d00288f3968ed2c19151
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/17191
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/northbridge/intel/i945/early_init.c

@@ -130,6 +130,7 @@ static void i945_detect_chipset(void)
 	reg8 = (pci_read_config8(PCI_DEV(0, 0x00, 0), 0xe4) & 0x07);
 	switch (reg8) {
 	case 0:
+	case 2:
 		printk(BIOS_DEBUG, "up to DDR2-667");
 		break;
 	case 3: