uboot-imx

mmc: Support bypass mode with the get_mmc_clk() method

Some SoCs want to adjust the input clock to the DWMMC block as a way of
controlling the MMC bus clock. Update the get_mmc_clk() method to support
this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>