[SCSI] aic94xx: Use sas_request_addr() to provide SAS WWN if the adapter lacks one

If the aic94xx chip doesn't have a SAS address in the chip's flash memory,
make libsas get one for us.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>