[SCSI] Fix ibmvscsi client for multiplatform iSeries+pSeries kernel

If you build a multiplatform kernel for iSeries and pSeries, with
ibmvscsic support, the resulting client doesn't work on iSeries.

This fixes that, using the appropriate low-level operations
for the machine detected at runtime.

[jejb: fixed up rejections around the srp transport patch]

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Acked by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>