ARM: tegra: paz00: Mark panel regulator as enabled on boot

Current U-Boot enables the display already. Marking the regulator as
enabled on boot fixes sporadic panel initialization failures.

Signed-off-by: Marc Dietrich <marvin24@gmx.de>
Tested-by: Misha Komarovskiy <zombah@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>