boot_device: Constify argument

Add const qualifier to first argument.

Change-Id: I6655e04401b6a7aa5cafb717ff6f46b80b96646e
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32703
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

src/lib/boot_device.c

@@ -20,7 +20,7 @@ void __weak boot_device_init(void)
 	/* Provide weak do-nothing init. */
 }
 
-int __weak boot_device_wp_region(struct region_device *rd,
+int __weak boot_device_wp_region(const struct region_device *rd,
 				 const enum bootdev_prot_type type)
 {
 	/* return a failure, make aware WP is not implemented */