Revert "drm: tegra: protect DC register access with mutex"

This reverts commit 83c0bcb694be31dcd6c04bdd935b96a95a0af548.

Lucas pointed out this was a mistake, and I missed the discussion,
so just revert it out to save a rebase.

Signed-off-by: Dave Airlie <airlied@redhat.com>
2 files changed