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>

src/arch/arm/include/armv7/arch/cpu.h

@@ -25,7 +25,7 @@
 
 struct cpu_driver {
 	struct device_operations *ops;
-	struct cpu_device_id *id_table;
+	const struct cpu_device_id *id_table;
 };
 
 struct thread;