mmc: tegra: Remove clk-name member from sdhci platform data

mmc: tegra: Remove clk-name member from sdhci platform data

- Removed clk-name data member from sdhci platform
as new clock driver doesn't require it to pass the clock
name through clk_get() APIs now.
- Removed FPGA specific code since limiting max
clock frequency for sdmmc is being done through
DT nodes now in T18x FPGA platform.

Bug 200102614
Bug 200103352

Change-Id: I22c9df2b000b85cf963db5285da86d9a636b6d72
Signed-off-by: R Raj Kumar <rrajk@nvidia.com>
Reviewed-on: http://git-master/r/746733
Reviewed-by: Venu Byravarasu <vbyravarasu@nvidia.com>