dts: npcx: re-arrange the default interrupt priority

Because the EC host command with SHI/SPI backend is timing sensitive, it
required the CPU to response the SHI interrrupt as soon as possible.
This commit re-arranges the default interrupt priority by:
1. keep the SHI's interrupt priority to 1.
2. Decrease the priority of the other peripherals by 1.
   (i.e. increase the priority `value` by 1)

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>