kinetis : Detect MCU flash parameters based on the SDID register.

kinetis : Detect MCU flash parameters based on the SDID register.

Try to detect the flash parameters based on the MCU SDID register. The hope
is that this works for K and KL series MCUs but it has only been tested on
a K21. YMMV.

Change-Id: Idfe71383a449065267f393b09ee3c3b24ac6a803
Signed-off-by: Per Ekman <pekenator@gmail.com>
Reviewed-on: http://openocd.zylin.com/1823
Tested-by: jenkins
Reviewed-by: Paul Fertser <fercerpav@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>