mmc: tegra: Update HW Tuning Iterations Value

mmc: tegra: Update HW Tuning Iterations Value

-Set HW Tuning Iterations to 256 in SDR50 mode.
-Set HW Tuning Iterations to 128 in non SDR50 modes.

Bug 1547083

Signed-off-by: Naveen Kumar Arepalli <naveenk@nvidia.com>
Reviewed-on: http://git-master/r/705357
(cherry picked from commit d97cae4f37c5ca1c946dd9ec2df96779506e513d)
Change-Id: Ia5dbac24963e6f111ce0feca77c1edb94ba97eaa
Signed-off-by: Pavan Kunapuli <pkunapuli@nvidia.com>
Reviewed-on: http://git-master/r/740016
Reviewed-by: Automatic_Commit_Validation_User