tree: Make internal variables static

All these variables are only used in the files they are defined in, so
they can be made static.

Change-Id: I1e55138adef540e9d3a2237aa5b289cb338c0608
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/33747
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/nicintel.c b/nicintel.c
index a4424e7..4672890 100644
--- a/nicintel.c
+++ b/nicintel.c
@@ -20,8 +20,8 @@
 #include "programmer.h"
 #include "hwaccess.h"
 
-uint8_t *nicintel_bar;
-uint8_t *nicintel_control_bar;
+static uint8_t *nicintel_bar;
+static uint8_t *nicintel_control_bar;
 
 const struct dev_entry nics_intel[] = {
 	{PCI_VENDOR_ID_INTEL, 0x1209, NT, "Intel", "8255xER/82551IT Fast Ethernet Controller"},