driver: espi: add notification and opcodes for ec host command support.

This CL add a new notification event, ESPI_PERIPHERAL_EC_HOST_CMD, and
two response opcodes, ECUSTOM_HOST_CMD_GET_PARAM_MEMORY and
ECUSTOM_HOST_CMD_SEND_RESULT, to connect with host command sub-system
between host and ec.

It also introduced three configurations to increase the flexibility of
ec host command settings:
1. ESPI_PERIPHERAL_HOST_CMD_DATA_PORT_NUM:
   Host I/O peripheral port number for ec host command data. The default
   value is 0x0200.
2. ESPI_PERIPHERAL_HOST_CMD_PARAM_PORT_NUM:
   Host I/O peripheral port number for ec host command parameters. The
   default value is 0x0800.

3. ESPI_NPCX_PERIPHERAL_HOST_CMD_PARAM_SIZE:
   Host I/O peripheral port size for ec host command in npcx series. The
   valid value in npcx ec series for this option is
   8/16/32/64/128/256/512/1024/2048/4096 bytes. The default value is 256
   bytes.

Signed-off-by: Mulin Chao <mlchao@nuvoton.com>