ibmvnic: remove unused ->wait_capability

With previous bug fix, ->wait_capability flag is no longer needed and can
be removed.

Fixes: 249168ad ("ibmvnic: Make CRQ interrupt tasklet wait for all capabilities crqs")
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Reviewed-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>