target: rename cortex_m3 to cortex_m

Rename cortex_m3 target to use a more correct cortex_m name.
This also adds a deprecated_name var so that older scripts issue a warning
to update the target name.

cfg files have also been updated to the new target name.

Change-Id: Ia8429f38e88da677249c5caa560c50f8ce56ea10
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/1129
Tested-by: jenkins
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>

src/rtos/ChibiOS.c

@@ -94,7 +94,7 @@ struct ChibiOS_params {
 
 struct ChibiOS_params ChibiOS_params_list[] = {
 	{
-	"cortex_m3",							/* target_name */
+	"cortex_m",							/* target_name */
 	0,
 	NULL,									/* stacking_info */
 	},