mmc: tegra: Ignore err if dvfs overrides are disabled

mmc: tegra: Ignore err if dvfs overrides are disabled

If dvfs overrides are disabled, continue tuning execution by
treating the dvfs override API return values as expected.

Bug 1516198

Change-Id: I8d27969029ce7b318d23c227e8dfb19793282fea
Signed-off-by: Pavan Kunapuli <pkunapuli@nvidia.com>
Signed-off-by: Naveen Kumar Arepalli <naveenk@nvidia.com>
Reviewed-on: http://git-master/r/413118
(cherry picked from commit 71edeee1a98a8dc7474781689b0859a32f5aca80)
Reviewed-on: http://git-master/r/416564
Reviewed-by: Bitan Biswas <bbiswas@nvidia.com>
Reviewed-by: Thomas Cherry <tcherry@nvidia.com>