qed: Revise alloc/setup/free flow

Re-organize the logic that allocates and frees memory of various
sub-components of the hw-function -

 a. No need to pass pointers to said structure as parameters;
    The internal logic knows exactly where to find/set the data.

 b. Nullify pointers after cleanup to prevent possible errors to
    re-entrant code.

Signed-off-by: Tomer Tayar <Tomer.Tayar@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>