netfilter: ebtables: split copy_everything_to_user into two functions

once CONFIG_COMPAT support is added to ebtables, the new
copy_counters_to_user function can be called instead of duplicating
code.

Also remove last use of MEMPRINT, as requested by Bart De Schuymer.

Signed-off-by: Florian Westphal <fw@strlen.de>