cpu/intel: Rename socket_mFCPGA478 to socket_m

The name was wrong. mFCPGA478 is actually a pseudonym for mPGA478MN,
the successor of the socket that was meant.

The official name of this socket is mPGA478MT. But "Socket M" is much
easier to distinguish.

Change-Id: I4efeaca69acddfcdc5e957b0b521544314d46eeb
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/31642
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
diff --git a/src/mainboard/ibase/mb899/devicetree.cb b/src/mainboard/ibase/mb899/devicetree.cb
index 3544c96..f81a68b 100644
--- a/src/mainboard/ibase/mb899/devicetree.cb
+++ b/src/mainboard/ibase/mb899/devicetree.cb
@@ -4,7 +4,7 @@
 	register "gfx.did" = "{ 0x80000100, 0x80000240, 0x80000410, 0x80000410, 0x00000005 }"
 
 	device cpu_cluster 0 on
-		chip cpu/intel/socket_mFCPGA478
+		chip cpu/intel/socket_m
 			device lapic 0 on end
 		end
 	end