zynq: sdhci: Define max clock by macro

zc1571 with silicon can operate on 200MHz maximum frequency. Setup this
frequency by default and fix setting for ep108.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/mmc/zynq_sdhci.c b/drivers/mmc/zynq_sdhci.c
index c69f5d4..e169b77 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, 52000000, 52000000 >> 9);
+	add_sdhci(host, CONFIG_ZYNQ_SDHCI_MAX_FREQ, 52000000 >> 9);
 	return 0;
 }