target/arm11: fix memory leaks, including register cache

target/arm11: fix memory leaks, including register cache

There is no deinit_target method, so few memory allocations leak
at openocd exit.
Issue identified by tracking all calls to arm_dpm_setup().

Implement the method arm11_dpm_deinit() to free all the memory
allocated in arm11_dpm_init() and call it in the new
arm11_deinit_target().

NOT TESTED on real HW.

Change-Id: Icab86e290fc2db14f70eb84c8286357aadb02a35
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5694
Tested-by: jenkins