tiny-printf: Add print_grouped_ull()

This function is used in the bootstage report which may be trigged in TPL
or TPL. Add a very basic implication of this function so that it builds.
There is no attempt to get the formatting right, since this would add too
much code size.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>