x4x boards: Factor out MAX_CPUS

LGA775 CPUs can have at most 4 threads, and Eaglelake supports them.
As this socket is also used by other chipsets, temporarily place this
symbol into the northbridge scope until all chipsets are factored out.

Change-Id: I6e01363d995e135815cc70779e0cd5baf806cf60
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41841
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

src/mainboard/intel/dg41wv/Kconfig

@@ -25,8 +25,4 @@ config MAINBOARD_PART_NUMBER
 	string
 	default "DG41WV"
 
-config MAX_CPUS
-	int
-	default 4
-
 endif # BOARD_INTEL_DG41WV

src/mainboard/intel/dg43gt/Kconfig

@@ -38,8 +38,4 @@ config MAINBOARD_PART_NUMBER
 	string
 	default "DG43GT"
 
-config MAX_CPUS
-	int
-	default 4
-
 endif # BOARD_INTEL_DG43GT