sb/intel/bd82x6x: Make `pch_silicon_supported` static

It's not needed anywhere else.

Change-Id: Ibc02e432bbc669b3fcfcb8add3c7b0c2a9f77d77
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44339
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/southbridge/intel/bd82x6x/pch.c

@@ -41,7 +41,7 @@ int pch_silicon_type(void)
 	return pch_type;
 }
 
-int pch_silicon_supported(int type, int rev)
+static int pch_silicon_supported(int type, int rev)
 {
 	int cur_type = pch_silicon_type();
 	int cur_rev = pch_silicon_revision();

src/southbridge/intel/bd82x6x/pch.h

@@ -42,7 +42,6 @@
 
 int pch_silicon_revision(void);
 int pch_silicon_type(void);
-int pch_silicon_supported(int type, int rev);
 void pch_iobp_update(u32 address, u32 andvalue, u32 orvalue);
 
 void enable_usb_bar(void);