ARM: tegra: norrin: Support DT variants w/wo DFLL data

ARM: tegra: norrin: Support DT variants w/wo DFLL data

Norrin platform can be used with different DT variants. Some of them
include DFLL device node, some - not. Added run-time check to Norrin
board file: continue with platform device registration only if DT DFLL
node is not present.

Bug 1442709

Change-Id: I4138392dd4e56d3812159783eb392fd2428d93ef
Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-on: http://git-master/r/372788
Reviewed-by: Adeel Raza <araza@nvidia.com>
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>