sunvdc: don't call VD_OP_GET_VTOC

The VD_OP_GET_VTOC operation will succeed only if the vdisk backend has a
VTOC label, otherwise it will fail. In particular, it will return error
48 (ENOTSUP) if the disk has an EFI label. VTOC disk labels are already
handled by directly reading the disk in block/partitions/sun.c (enabled by
CONFIG_SUN_PARTITION which defaults to y on SPARC). Since port->label is
unused in the driver, remove the call and the field.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>