There is no difference between 4k erase and sector erase.
But sector erase would previously do `.block_erase` which would not
erase a sector (4k) but a whole block (64k).
Fortunately all boards declare `SPI_NOR_F_SECT_4K` and all file systems
don't try to erase anything smaller, so this was never triggered.
Add an `assert(0)` to crash instead of corrupting data.
Unify cpu_init for all Kinetis CPUs to reduce code duplication.
Updated the MCG driver implementation to make the configuration easier.
Most clock settings are initialized by kinetis_mcg_init() called from
cpu_init. Board specific external clock source initialization
(FRDM-K64F, PhyNode) needs to be performed in board_init instead of
in cpu_init.
The CPU has multiple issues and several parts of the platform code
does not even compile cleanly for this CPU in the current state.
This removes support for parts MK60DN256ZVLL10, MK60DN512ZVLL10
(note the Z) CPUs with this part number were used in Mulle v0.60 which
only has been used in some in-house projects at Eistec and LTU.
Initially supports only Mulles with serial number > 220 (due to missing
MK60DN256ZVLL10 support in k60).
See also: https://github.com/RIOT-OS/RIOT/wiki/Board%3A-Mulle
Signed-off-by: Joakim Gebart <joakim.gebart@eistec.se>