mmc: zynq_sdhci: Fix SDx_BASECLK configuration

mmc: zynq_sdhci: Fix SDx_BASECLK configuration

The DLL mode supported SD reference clocks are 50 MHz, 100 MHz and
200 MHz. When user select SD frequency as 200MHz in the design, the
actual frequency is going to come around ~187MHz (<= 200MHz considering
the parent clock and divisor selection). We need to set SDx_BASECLK as
200 in this case, setting 187 will result in tuning failures in mmc.

Set SDx_BASECLK to exact value of 200, 100 or 50 based on the frequency
range.

Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Link: https://lore.kernel.org/r/6c1e5eeeedd2864a0c85e6b409d182031d8c6c1a.1648210268.git.michal.simek@xilinx.com