mmc: sd: add support for UHS card to get max frequency

This change adds UHS cards to mmc_sd_get_max_clock() API.
Cards that support UHS can set timing of SDR104 which
supports frequency up to 208Mhz.

Change-Id: I25bcb35aa2cecd98f6f04cd98a616a76c75b6784
Signed-off-by: Talel Shenhar <tatias@codeaurora.org>