ofproto: Inline trivial functions.

ofproto: Inline trivial functions.

rule_dpif_is_internal is among the top ten OVS internal functions in
recent perf reports.  Inline it and some other equally trivial
functions.

This change removes rule_is_internal(), since the fact that a table is
an internal one is defined within ofproto-dpif, not ofproto.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>