hpsa: avoid unneccesary calls to resource freeing functions

If hpsa_allocate_cmd_pool failed, we were calling two functions unnecessarily:

  hpsa_free_sg_chain_blocks(h);
  hpsa_free_cmd_pool(h);

This didn't cause any problem, as those functions can tolerate being called
when what they free hasn't been allocated (relevant pointers would be NULL)
but it is potentially confusing.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Signed-off-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>