tree: Make internal functions static

None of these functions are used outside of the files they are defined
in, so make them all static.

Change-Id: Ie9cbe12d289bcedacf2f1bf483ae64ef8039ccc1
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/33667
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/pcidev.c b/pcidev.c
index f5ad819..54c1fd3 100644
--- a/pcidev.c
+++ b/pcidev.c
@@ -266,7 +266,7 @@
 	};
 };
 
-int undo_pci_write(void *p)
+static int undo_pci_write(void *p)
 {
 	struct undo_pci_write_data *data = p;
 	if (pacc == NULL || data->dev == NULL) {