ARM: tegra: dalmore - Add DSI power supply

The 1.2V supply for CSI and DSI was previously marked always-on. This is
suboptimal because it prevents the supply from being disabled when there
is no activity in the display or capture paths that it powers.

Hook up the regulator to the DSI output and mark it as not always-on, so
that it will only be enabled when DSI actually needs it.

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