mb/lenovo/t400: use socket mPGA478MN instead of BGA945

The T400 features a socket P (mPGA478MN) and could potentially support
model_6fx CPUs.

Change-Id: I24f3356aa213c29011953daed31f46404e7a4d9d
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/17155
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/lenovo/t400/Kconfig

@@ -3,7 +3,7 @@ if BOARD_LENOVO_T400 || BOARD_LENOVO_T500 || BOARD_LENOVO_R400
 config BOARD_SPECIFIC_OPTIONS # dummy
 	def_bool y
 	select SYSTEM_TYPE_LAPTOP
-	select CPU_INTEL_SOCKET_BGA956
+	select CPU_INTEL_SOCKET_MPGA478MN
 	select NORTHBRIDGE_INTEL_GM45
 	select SOUTHBRIDGE_INTEL_I82801IX
 	select EC_LENOVO_PMH7

src/mainboard/lenovo/t400/devicetree.cb

@@ -6,7 +6,7 @@ chip northbridge/intel/gm45
 	register "gfx.use_spread_spectrum_clock" = "1"
 
 	device cpu_cluster 0 on
-		chip cpu/intel/socket_BGA956
+		chip cpu/intel/socket_mPGA478MN
 			device lapic 0 on end
 		end
 		chip cpu/intel/model_1067x