driver: flash: npcx: add support for npcx4 series

This CL introduces new Flash Interface Unit (FIU) hardware in npcx4
series. The different operations of npcx9 and npcx4 FIU include:

1. 4-byte mode support for DRA mode move to SPI_DEV reg
2. To access the second flash in DRA mode, we need to configure
   SPI_DEV_SEL field in BURST_CFG additionally.

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