mmc: core: Removed workaround for SD card SDR104 CRC handling

Remove the workaround for SD card's SDR104 mode CRC error handling.
The SD card's SDR104 mode CRC errors issue was seen on some
SDCC controllers and the software reduced the SD card clock speed
as a workaround to avoid CRC errors. The latest SDCC controller
does not have this issue, so removing the workaround.

Change-Id: I3638500c83f7a6a2f9e4eae28a3179eea1d1fc89
Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>