target: fix memory leaks on targets based on arm9tdmi

target: fix memory leaks on targets based on arm9tdmi

Similarly to the fix for arm926ejs (also base on arm9tdmi), fix
the other targets based on arm9tdmi.
The fix for arm926ejs is tested on SPEAr320 target.

This fix is proposed separately because is not tested on a correct
target device, but tested on SPEAr320 by hacking the target type
and pretending it is the correct one, e.g.:
	sed -i s/arm926ejs/arm920t/ tcl/target/spear3xx.cfg

The memory leaks detected and fixed are:
- arm register cache;
- EmbeddedICE register cache;
- arm_jtag_reset_callback internal data;
- struct <target_type>_common.

Change-Id: I565f9a5bf144a9df78474434d86a64127ef0fbe5
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5699
Tested-by: jenkins