powerpc: Tidy up dma_map_ops after adding new hook

The new get_required_mask hook name is longer than many of but not all
of the prior ops.  Tidy the struct initializers to align the equal signs
using the local whitespace.
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Cc: benh@kernel.crashing.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>