isci: Remove SCIC_SWAP_DWORD()

Use Linux native swab32() call instead of SCIC_SWAP_DWORD().

We need to swab() because the hardware munges the data into a
"big-endian dword" stream which is byte-swapped from the sas definition
regardless of host endian.

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