powerpc: remove the legacy iSeries part of ibmvscsi

The PowerPC legacy iSeries platform is being removed and this code is
no longer selectable.  There is more clean up that can be done, but this
just gets the old code out of the way.

Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Brian King <brking@linux.vnet.ibm.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>