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>

tcl/target/kx.cfg

@@ -33,14 +33,6 @@ swj_newdap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPU
 set _TARGETNAME $_CHIPNAME.cpu
 target create $_TARGETNAME cortex_m -chain-position $_CHIPNAME.cpu
 
-# It is important that "kinetis mdm check_security" is called for
-# 'examine-end' event and not 'eximine-start'. Calling it in 'examine-start'
-# causes "kinetis mdm check_security" to fail the first time openocd
-# calls it when it tries to connect after the CPU has been power-cycled.
-$_CHIPNAME.cpu configure -event examine-end {
-	kinetis mdm check_security
-}
-
 $_TARGETNAME configure -work-area-phys 0x20000000 -work-area-size $_WORKAREASIZE -work-area-backup 0
 
 set _FLASHNAME $_CHIPNAME.flash
@@ -51,6 +43,11 @@ adapter_khz 1000
 reset_config srst_nogate
 
 if {![using_hla]} {
+   # Detect secured MCU or boot lock-up in RESET/WDOG loop
+   $_CHIPNAME.cpu configure -event examine-start {
+      kinetis mdm check_security
+   }
+
    # if srst is not fitted use SYSRESETREQ to
    # perform a soft reset
    cortex_m reset_config sysresetreq