isci: fix isci_pci_probe() generates warning on efi failure path

The oem parameter image embedded in the efi variable is at an offset
from the start of the variable.  However, in the failure path we try to
free the 'orom' pointer which is only valid when the paramaters are
being read from the legacy option-rom space.

Since failure to load the oem parameters is unlikely and we keep the
memory around in the success case just defer all de-allocation to devm.

Cc: <stable@vger.kernel.org>
Reported-by: Don Morris <don.morris@hp.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>