nb/intel/x4x: Move register headers into a subfolder

Move all files with register definitions into a `registers` subfolder.
Subsequent commits will move the remaining registers into this folder.

Tested with BUILD_TIMELESS=1, Asus P5QL PRO does not change.

Change-Id: I74dbd985b980d8a42bfaf2984820005320a803d3
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/45421
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/northbridge/intel/x4x/x4x.h b/src/northbridge/intel/x4x/x4x.h
index c624287..2534575 100644
--- a/src/northbridge/intel/x4x/x4x.h
+++ b/src/northbridge/intel/x4x/x4x.h
@@ -11,7 +11,7 @@
  */
 #define HOST_BRIDGE	PCI_DEV(0, 0, 0)
 
-#include "hostbridge_regs.h"
+#include "registers/host_bridge.h"
 
 /*
  * D1:F0 PEG