arm: lpcxpresso54114_m0: Add board support for slave core

Add a board port to allow creation of "firmware" code that will run on
the slave core (Cortex-M0+).

Origin: Original

Signed-off-by: Stanislav Poboril <stanislav.poboril@nxp.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>