ofp-errors: Remove OFPERR_NXBIC_DUP_TYPE

ofp-errors: Remove OFPERR_NXBIC_DUP_TYPE

OFPERR_NXBIC_DUP_TYPE is currently only used in
decode_openflow11_instructions() which is part of a non-NX extension
portion of the Open Flow 1.1+ implementation.

After recent discussion it has been decided to attempt to only use
standardised, albeit less-specific, errors unless errors arise from use of
an NX extension.

With the above in mind it seems appropriate to:
* Use OFPERR_OFPIT_BAD_INSTRUCTION in place of OFPERR_NXBIC_DUP_TYPE.
* Remove OFPERR_NXBIC_DUP_TYPE as it is no longer used.

An unfortunate side-effect of this change is that the error for
the case in question is now less-specific.

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