board: npcx: add npcx9m6f_evb board.

Introduce the npcx9m6f_evb board driver. NPCX9M6F_EVB board is a
development platform to evaluate the Nuvoton NPCX9 series
microcontrollers. This board needs to be mated with part number
NPCX996F.

It also includes:
 1. Add CONFIG_BOARD_NPCX9M6F_EVB definition for adc test suite.
 2. Add npcx7m6f_evb.overlay file for gpio test suite.

Signed-off-by: Jun Lin <CHLin56@nuvoton.com>
Signed-off-by: Mulin Chao <mlchao@nuvoton.com>
11 files changed