watchdog: WDT standard driver API support

- Porting standard WDT driver and APIs.
- Create a demo scenario with background WDT, WDT2.
- Solve boot up problem when warn reboot is triggered.

Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Change-Id: Ic2b823fc46f3789f5e378d8f84c2c2e49aa735c0

Author: chintingkuo

drivers/spi/spi_monitor_aspeed.c

@@ -1244,6 +1244,8 @@ static int aspeed_spi_monitor_init(const struct device *dev)
 
 	/* always enable internal passthrough configuration */
 	spim_scu_passthrough_mode(dev, 0, true);
+	/* always keep at master mode during booting up stage */
+	spim_ext_mux_config(dev, SPIM_MASTER_MODE);
 
 	if (config->extra_clk_en)
 		spim_block_mode_config(dev, SPIM_BLOCK_EXTRA_CLK);