zynq: sdhci: Calculate minimum frequency based on max frequency

Calculate the minimum sd clock based on max clock. This will
be done by add_sdhci() if we pass minimum clock as zero.
It also does based on SD host contoller version.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/mmc/zynq_sdhci.c b/drivers/mmc/zynq_sdhci.c
index e169b77..2d6cb31 100644
--- a/drivers/mmc/zynq_sdhci.c
+++ b/drivers/mmc/zynq_sdhci.c
@@ -29,7 +29,7 @@
 		       SDHCI_QUIRK_BROKEN_R1B;
 	host->version = sdhci_readw(host, SDHCI_HOST_VERSION);
 
-	add_sdhci(host, CONFIG_ZYNQ_SDHCI_MAX_FREQ, 52000000 >> 9);
+	add_sdhci(host, CONFIG_ZYNQ_SDHCI_MAX_FREQ, 0);
 	return 0;
 }