drm/tegra: dc: Fix possible_crtcs mask for planes

Cursor and overlay planes use a possible_crtcs mask based on the DC pipe
number. However, DRM requires each bit in the mask to correspond to the
index of the CRTC, which will be different from the DC pipe number for a
configuration where the first display controller is disabled, or where a
deferred probe leads to the first display controller being probed after
the first.

Suggested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>