flash Kinetis: fix probe for FlexNVM partitioned as EEPROM backup

flash Kinetis: fix probe for FlexNVM partitioned as EEPROM backup

If a MCU has FlexNVM partitioned as EEPROM backup only
(no data flash), kinetis_probe_chip() detects zero fcfg2_maxaddr1
and adjusts flash banks count to 1, what is obviously wrong.

The change limits the test to devices without FlexNVM.

Computation of program flash/FlexNVM blocks is now more robust.

Missing case 0x07 is added to switch (fcfg1_depart)

Change-Id: I0bd6030a0fe1ab62aeb0223bbdf2aee1505bf6a0
Reported-by: simon.haines@scalardata.com
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4180
Tested-by: jenkins
Reviewed-by: Simon Haines <simon.haines@scalardata.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>