[SCSI] aacraid: rework communication support code

Received from Mark Salyzyn,

Replace all if/else communication transports with a platform function call.
This is in recognition of the need to migrate to up-and-coming transports.
Currently the Linux driver does not support two available communication
transports provided by our products, these will be added in future patches, and
will expand the platform function set.

Signed-off-by Mark Haverkamp <markh@linux-foundation.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>