[SCSI] fc_transport: Generalize WWN to u64 interger conversions.

On some platforms the hard-casting of 8 byte node_name and
port_name arrays to an u64 would cause unaligned-access
warnings.  Generalize the conversions with a transport
helper function which performs consistent shifting of WWN
bytes.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>