[U-Boot] boots (subcommands)

[Kumar Gala]

So after refactoring the bootm code I get to the following "sub  
command set":

* interrupt on/off (to enable/disable interrupts)
* icache/dcache (already exists)
* usb stop (already exists)
* boots (boot sub command):
	start <ARGS> - takes same args as bootm, parses the args and sets up  
bootm_headers_t
	load_os - decompresses and loads OS image
	relocate_initrd - relocates initrd based on constraints
	relocate_fdt	- relocates fdt based on constraints
	jump

(load_os, relocate_initrd, relocate_fdt, jump will fail if start has  
been called, beyond that they can be called in any order and its left  
to the user to do the right thing).

* fdt:
	chosen -- expand to allow setting initrd info
	boardsetup -- exists
	resize - new

We might need one or two other commands to prep things for the OS and  
some bd related foo.

- k