etm: fix warning by removing assignment that is immediately overwritten

Change-Id: Ia3a83d3c1fc3a1707d69017fce6cf142a81babc4
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Reviewed-on: http://openocd.zylin.com/165
Tested-by: jenkins
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/target/etm.c

@@ -314,7 +314,6 @@ struct reg_cache *etm_build_reg_cache(struct target *target,
 
 	/* figure ETM version then add base registers */
 	if (config & (1 << 31)) {
-		bcd_vers = 0x20;
 		LOG_WARNING("ETMv2+ support is incomplete");
 
 		/* REVISIT more registers may exist; they may now be