[U-Boot] Improve default "make" targets (ALL-y)

[Loïc Minier]

On Fri, Nov 11, 2011, Mike Frysinger wrote:
> 	- ignore: u-boot u-boot.{map,lds,srec,ihex}
> 	- if there is a file other than u-boot.bin, you probably want that
> 	- otherwise, you want u-boot.bin

 These are decent rules; plus SPL files I guess, and perhaps DTB
 versions.

 What did you think of some kind of "install" or "dist" rule?

-- 
Loïc Minier