ARM: tegra: dvfs: Update rail relationships support

ARM: tegra: dvfs: Update rail relationships support

- Since nominal and suspend voltage levels can be different, defined
relationship solved_at_suspend flag (in addition to solved_at_nominal).

- Since, overriding dependent rail below nominal voltage may not be
safe set minimum override boundary to nominal level for any rail that
depends on other rail.

Bug 1461646

Change-Id: I1fee3380d16da3f0feeec26d91df0fb8723946b4
Signed-off-by: Alex Frid <afrid@nvidia.com>
Reviewed-on: http://git-master/r/369084
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>