flash Kinetis: Detect RESET/WDOG loop, fix detection of secured MCU

flash Kinetis: Detect RESET/WDOG loop, fix detection of secured MCU

Kinetis driver checks MDM STAT register to detect secured state of MCU.
Original version often reported a blank device as secured one.
Change #3010 has not fixed all false reports.
After changes in arm_adi_v5 infrastructure secured devices was not detected
at all.

New algorithm uses multiple MDM STAT reads and counts MDM_STAT_SYSSEC and
MDM_STAT_FREADY bits. Both secured MCU and MCU locked-up in RESET/WDOG loop
are detected reliably.

Detection is run in both kx.cfg and klx.cfg from examine-start event,
not examine-end as before. Event is configured only for non hla adapter.

Minor fix in klx.cfg: commented out adapter_khz 24000 in reset-init.
Such frequency is not supported in VLPR CPU mode and with JTAG.

Change-Id: I2ec2b68c45bde9898159cd15fbdcbcfa538c41d9
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/3547
Tested-by: jenkins
Reviewed-by: Steven Stallion <stallion@squareup.com>
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>