powerpc/powernv: Fix the log message when disabling VF

On powernv platform, IOV BAR would be shifted if necessary. While the log
message is not correct when disabling VFs.

This patch fixes this by print correct message based on the offset value.

Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>