intel: Define `RCBA_LENGTH` in Kconfig and use it

Change-Id: Ief81d49f04c1743b2a37633c4a35da9d6ddb0974
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50039
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/sandybridge/acpi/sandybridge.asl b/src/northbridge/intel/sandybridge/acpi/sandybridge.asl
index 16bcd54..5d7a777 100644
--- a/src/northbridge/intel/sandybridge/acpi/sandybridge.asl
+++ b/src/northbridge/intel/sandybridge/acpi/sandybridge.asl
@@ -10,7 +10,7 @@
 	Name (_UID, 1)
 
 	Name (PDRS, ResourceTemplate() {
-		Memory32Fixed(ReadWrite, CONFIG_FIXED_RCBA_MMIO_BASE, 0x00004000)
+		Memory32Fixed(ReadWrite, CONFIG_FIXED_RCBA_MMIO_BASE, CONFIG_RCBA_LENGTH)
 		// Filled by _CRS
 		Memory32Fixed(ReadWrite, 0, 0x00008000, MCHB)
 		Memory32Fixed(ReadWrite, 0, 0x00001000, DMIB)