cleanup: rename armv4_5 to arm for readability

Nothing more than a name change, just to make reading
the code a bit simpler.

Change-Id: I73a16b7302b48ce07d9688162955aae71d11eb45
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/390
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>

src/target/arm926ejs.h

@@ -42,7 +42,7 @@ static inline struct arm926ejs_common *
 target_to_arm926(struct target *target)
 {
 	return container_of(target->arch_info, struct arm926ejs_common,
-			arm7_9_common.armv4_5_common);
+			arm7_9_common.arm);
 }