soc/intel/xeon_sp: Allocate resources above 4G

This makes sure that prefetchable mem64 memory gets allocated above 4G
which allows non prefetchable resources to be allocated in the tight
window below 4G.

TEST=intel/archercity CRB

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: I27d4f9ce91c12ed4ab3b2f18f2a92b742115d275
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79058
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Shuo Liu <shuo.liu@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/xeon_sp/Kconfig

@@ -91,6 +91,9 @@ config ECAM_MMCONF_BASE_ADDRESS
 config ECAM_MMCONF_BUS_NUMBER
 	default 256
 
+config ALWAYS_ALLOW_ABOVE_4G_ALLOCATION
+	default y
+
 config HEAP_SIZE
 	hex
 	default 0x80000