clk: tegra: fix sdmmc clks on Tegra1x4

The sdmmc clocks on Tegra114 and Tegra124 are 3-bit wide muxes with
6 parents.  Add support for tegra_clk_sdmmc*_8 and switch Tegra114
and Tegra124 to use these clocks instead.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>