lib: Inline functions used in classifier_lookup.

lib: Inline functions used in classifier_lookup.

This helps about 1% in TCP_CRR performance test.  However, this also
helps by clearly showing the classifier_lookup() cost in perf reports
as one item.

This also cleans up the flow/match APIs from functionality only used
by the classifier, making is more straightforward to evolve them
later.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>