powerpc/pseries/ddw: simplify enable_ddw()

powerpc/pseries/ddw: simplify enable_ddw()

[ Upstream commit fb4ee2b30cd09e95524640149e4ee0d7f22c3e7b ]

This drops rather useless ddw_enabled flag as direct_mapping implies
it anyway.

While at this, fix indents in enable_ddw().

This should not cause any behavioral change.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211108040320.3857636-3-aik@ozlabs.ru
Stable-dep-of: 3bf983e4e93c ("powerpc/pseries/iommu: enable_ddw incorrectly returns direct mapping for SR-IOV device")
Signed-off-by: Sasha Levin <sashal@kernel.org>