datapath: Use "OVS_*" as opposed to "ODP_*" for user<->kernel interactions.

datapath: Use "OVS_*" as opposed to "ODP_*" for user<->kernel interactions.

The prefix "ODP_*" is not overly descriptive in the context of the
larger Linux tree.  This commit changes the prefix to "OVS_*" for the
userpace to kernel interactions.  The userspace libraries still use
"ODP_" in many of their interfaces since it is more descriptive in the
OVS oeuvre.

Feature #6904

Signed-off-by: Justin Pettit <jpettit@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>