Execution times in early boot and AUX timing

[Werner Almesberger]

Some lazy bastard wrote wrote:
>   I didn't measure this directly, [...]

Okay, here's the missing data:

NAND boot:
	falling edge of POWER to IO_3V3 up:	 43ms
	IO_3V3 to start:			  2ms
	start: to done_relocate:		127ms

	total:					172ms

NOR boot:
	falling edge of POWER to IO_3V3 up:	 43ms
	IO_3V3 to start:			 <1ms
	start: to done_relocate:		 55ms

	total:					 98ms

So my original approximations were about 22ms too short. This changes
the boot to NAND menu instructions from

>   - wait 1s (more than 150ms, less than 2.8s)

to

>   - wait 1s (more than 175ms, less than 2.8s)

- Werner