[U-Boot] [PATCH] Makefile: drop mention of *.cfgtmp

[Trent Piepho]

On Mon, 2018-06-18 at 06:57 +0300, Baruch Siach wrote:
> Since commit f916757300 (imx: Create distinct pre-processed mkimage
> config files), *.cfgtmp files are no longer generated. There is no need
> to remove them on the 'clean' target anymore.
> 
> Remove also the .gitignore glob.

I didn't think of the gitignore file when I did that patch.  While I
did stop generating .cfgtmp files, I replaced them with .cfgout files. 
So the gitignore patch should really be a s/cfgtmp/cfgout/ I think.

It shouldn't be necessary to add *.cfgout to the find command since
they are added to the target list and cleaned that way.