board: nxp_ls1046ardb: add 2 cores smp for running in Jailhouse

1. add a seperate 2 cores SMP board configuration to run in Jailhouse
   inmate Cell, root Cell Linux will use Core0 and Core1, Zephyr will
   run on Core2 and Core3.
2. Refine the code of dts, move SoC common dts nodes into dtsi fiel in
   dts/arm64/nxp/ directory.
3. Add myself to be code owner of directory dts/arm64/nxp/.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>