ext: Add dual core startup code for lpc54114 based on mcux 2.3.0

The new file startup_LPC54114_cm4.S is a copy of the file
devices/LPC54114/gcc/startup_LPC54114_cm4.S from mcux 2.3.0.
It contains platform specific initialization code for both cores.

Origin: NXP MCUXpresso SDK 2.3.0
URL: mcux.nxp.com
Maintained-by: External

Signed-off-by: Stanislav Poboril <stanislav.poboril@nxp.com>