netfilter: nf_tables: fix goto action

This patch fixes a crash when trying to access the counters and the
default chain policy from the non-base chain that we have reached
via the goto chain. Fix this by falling back on the original base
chain after returning from the custom chain.

While fixing this, kill the inline function to account chain statistics
to improve source code readability.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>