openflow: Split OFPAT_* into OFPAT10_* and OFPAT11_*.

openflow: Split OFPAT_* into OFPAT10_* and OFPAT11_*.

An upcoming commit will start referring to OpenFlow 1.1 actions, which are
renumbered relative to OpenFlow 1.0 actions, so this commit prepares by
changing all the existing uses of OFPAT_* to instead use OFPAT10_*.

This commit also introduces the OFPAT11_* constants.

Reviewed-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ben Pfaff <blp@nicira.com>