nb/intel/sandybridge: Move southbridge code to bd82x6x

Move the southbridge code to bd82x6x folder similar to the lynxpoint
implementation.

Tested on Lenovo T520 (Intel Sandy Bridge).
Still boots to OS, no errors visible in dmesg.

Change-Id: I8afc9f966033f45823f5dfde279e0f66de165e93
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32035
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/southbridge/intel/bd82x6x/pch.h b/src/southbridge/intel/bd82x6x/pch.h
index 7419965..21b6031 100644
--- a/src/southbridge/intel/bd82x6x/pch.h
+++ b/src/southbridge/intel/bd82x6x/pch.h
@@ -76,6 +76,7 @@
 void southbridge_rcba_config(void);
 void mainboard_rcba_config(void);
 void early_pch_init_native(void);
+void early_pch_init(void);
 
 struct southbridge_usb_port
 {