target/arc: Introduce Actionpoints support

target/arc: Introduce Actionpoints support

Actionpoint mechanism allows to setup HW breakpoints and watchpoints on Synopsys ARC CPUs.
This mechanism is controlled by DEBUG register and by a set of auxilary registers.
Each actionpoint is controlled by 3 aux registers: Actionpoint(AP) match mask(AP_AMM),
AP match value(AP_AMV) and AP control(AC).

Note: some fields of actionpoint_t structure will be used in further
support of watchpoints.

Change-Id: I4efb24675f247cc19d9122501c9e63c3126fcab4
Signed-off-by: Evgeniy Didin <didin@synopsys.com>
Reviewed-on: http://openocd.zylin.com/5763
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>