poplar: clean up board level mmc initialization code

We have converted mmc to driver model on Poplar.  So let's clean up
board level mmc initialization code.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
3 files changed