Watchdog driver general info

CONFIG_HW_WATCHDOG
	This enables hw_watchdog_reset to be called during various loops,
	including waiting for a character on a serial port. But it
	does not also call hw_watchdog_init. Boards which want this
	enabled must call this function in their board file. This split
	is useful because some rom's enable the watchdog when downloading
	new code, so it must be serviced, but the board would rather it
	was off. And, it cannot always be turned off once on.

CONFIG_WATCHDOG_TIMEOUT_MSECS
	Can be used to change the timeout for i.mx31/35/5x/6x.
	If not given, will default to maximum timeout. This would
	be 128000 msec for i.mx31/35/5x/6x.

CONFIG_WDT_AT91
	Available for AT91SAM9 to service the watchdog.

CONFIG_IMX_WATCHDOG
	Available for i.mx31/35/5x/6x to service the watchdog. This is not
	automatically set because some boards (vision2) still need to define
	their own hw_watchdog_reset routine.
	TODO: vision2 is removed now, so perhaps this can be changed.

CONFIG_XILINX_TB_WATCHDOG
	Available for Xilinx Axi platforms to service timebase watchdog timer.