ARM64: dma-mapping: fix build regression

The Merge remote-tracking branch 'remotes/freedreno/for-integration-
drm-msm-next-working-clean-plus' and commit
"WIP: maybe? fallback to swiotlb ops" add a build regression
so revert the change.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>