kinetis: update support for all program flash granularities

kinetis: update support for all program flash granularities

Updates the Kinetis NOR flash support to handle all known block and sector
sizes.  Previously only 2kiB sectors were hard-coded, now all four known
combinations non-volatile sector sizes are supported.

The premise of separating Kinetis Program Flash (PFLASH) from FlexNVM is
also introduced.  This means each "block" of flash (in Freescale terms) is
treated as a bank in OpenOCD.  Correspondingly, the existing board
configuration for the TWR-K60M512 eval system is updated to recognize two
banks instead of one.

A board config for the TWR-K60F120M is also added.

Bank and sector erase and programming has been checked with both of the
mentioned eval boards.

Change-Id: Iae2d10ebf8f548d0a3698df5430bbbe1ccadc58a
Signed-off-by: Christopher Kilgour <techie@whiterocker.com>
Reviewed-on: http://openocd.zylin.com/663
Tested-by: jenkins
Reviewed-by: Mathias Küster <kesmtp@freenet.de>
Reviewed-by: Jan Dakinevich <jan.dakinevich@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>