mb/lenovo/s230u: Don't write BUC and beyond

The BUC register is actually only 8 bits wide and setting bit 5
(disabling GbE) is already done by generic code.

Change-Id: I4b8e14606c319e8bfc48d6757087f28af1bd5dfb
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36894
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/mainboard/lenovo/s230u/early_init.c

@@ -40,11 +40,6 @@ void mainboard_pch_lpc_setup(void)
 		ec_mm_set_bit(0x3b, 4);
 }
 
-void mainboard_late_rcba_config(void)
-{
-	/* Disable devices.  */
-	RCBA32(BUC) = 0x00000020;
-}
 const struct southbridge_usb_port mainboard_usb_ports[] = {
 	{ 1, 1, 0 },
 	{ 1, 0, 0 },