mmc: sdhci-pxav3: controller should use SDCLK for timeout calculation

sdhci-pxav3 host controller used SDCLK for data timeout.

Signed-off-by: Kevin Liu <kliu5@marvell.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Chris Ball <cjb@laptop.org>