dts: boards: Define dts aliases at soc level for kinetis socs

Defines device tree aliases for on-chip peripherals at the soc level
instead of the board level for all kinetis socs. The eliminates some
duplicate code in the board level device trees, and will allow drivers
to use device-tree generated macros directly instead of through dts
fixups.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>