Constify struct cpu_device_id instances

There is currently no case where a struct cpu_device_id instance needs
to be modified. Thus, declare all instances as const.

Change-Id: I5ec7460b56d75d255b3451d76a46df76a51d6365
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/22526
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
diff --git a/src/arch/x86/cpu.c b/src/arch/x86/cpu.c
index ff82661..cfcfdbd 100644
--- a/src/arch/x86/cpu.c
+++ b/src/arch/x86/cpu.c
@@ -203,7 +203,7 @@
 {
 	struct cpu_driver *driver;
 	for (driver = _cpu_drivers; driver < _ecpu_drivers; driver++) {
-		struct cpu_device_id *id;
+		const struct cpu_device_id *id;
 		for (id = driver->id_table;
 		     id->vendor != X86_VENDOR_INVALID; id++) {
 			if ((cpu->vendor == id->vendor) &&