libibverbs: remove duplicate wc status values

Several ibv_wc_status values map to the same winverbs wc status
values.  This causes an error if the ibv_wc_status values are
referenced in a switch statement.  Replace the duplicated values
with constants, so every wc status value is unique.

Since the wc status values are mapped from the provider library,
the duplicated values are not used anyway.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>