mmc: tegra: remove redundant return statement

A redundant return statement is removed from
tegra_sdhci_set_uhs_signaling(). The function returns void and the
return does not affect the control flow of the function.

Signed-off-by: Aapo Vienamo <aapo.vienamo@iki.fi>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>