isci: Move firmware loading to per PCI device

Moved the firmware loading from per adapter to per PCI device. This should
prevent firmware from being loaded twice becuase of 2 SCU controller per
PCI device. We do have to do it per PCI device because request_firmware()
requires a struct device passed in.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>