iommu/ipmmu-vmsa: Change IOMMU_EXEC to IOMMU_NOEXEC

Commit a720b41c ("iommu/arm-smmu: change IOMMU_EXEC to
IOMMU_NOEXEC") has inverted and replaced the IOMMU_EXEC flag with
IOMMU_NOEXEC. Update the driver accordingly.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>