drm/tegra: dc: Move register definitions into a table

After commit 67e04d1a

 ("drm/tegra: dc: Trace register accesses"),
the debugfs register dump implementation causes excessive stack usage
and can result in build warnings. To fix this, move the register
definitions into a table and iterate over the table while dumping the
registers to debugfs.

Signed-off-by: Thierry Reding <treding@nvidia.com>