mmc/dw_mmc: Fix clock divider calculation error for bypass mode

mmc/dw_mmc: Fix clock divider calculation error for bypass mode

To fix the clock divider calculation error when the controller
clock same as the operating frequency. This is known as bypass
mode. In this mode, the divider should be 0.

Signed-off-by: Chin Liang See <clsee@altera.com>
Cc: Pantelis Antoniou <panto@antoniou-consulting.com>
Cc: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Mischa Jonker <mjonker@synopsys.com>