qed: Fix SPQ entries not returned to pool in error flows

qed_sp_destroy_request() API was added for SPQ users that need to
free/return the entry they acquired in their error flows.

Signed-off-by: Denis Bolotin <denis.bolotin@cavium.com>
Signed-off-by: Michal Kalderon <michal.kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>