extensions: prefer plain 'set' over 'set mark and'

extensions: prefer plain 'set' over 'set mark and'

adding a test case for MARK --set-mark 0 fails with
exp: nft add rule ip mangle OUTPUT counter meta mark set 0x0
res: nft add rule ip mangle OUTPUT counter meta mark set mark and 0x0

This translation isn't wrong, but unneccessarily complex, so
change order to first check if mask bits are all ones.

In that case we can simply use an immediate value without
need for logical operators.

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