axs10x/emdk/hsdk/iot_dk: Implement board_mmc_getcd()

So now we may detect MMC/SD-card existence and
instead of completely misleading message on missing card:
------------------------>8-----------------------
Loading Environment from FAT... Card did not respond to voltage select!
------------------------>8-----------------------

we now get very clear one:
------------------------>8-----------------------
Loading Environment from FAT... MMC: no card present
------------------------>8-----------------------

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/board/synopsys/emdk/emdk.c b/board/synopsys/emdk/emdk.c
index bbb946a..79cafef 100644
--- a/board/synopsys/emdk/emdk.c
+++ b/board/synopsys/emdk/emdk.c
@@ -34,6 +34,13 @@
 	return 0;
 }
 
+int board_mmc_getcd(struct mmc *mmc)
+{
+	struct dwmci_host *host = mmc->priv;
+
+	return !(dwmci_readl(host, DWMCI_CDETECT) & 1);
+}
+
 #define CREG_BASE		0xF0001000
 #define CREG_BOOT_OFFSET	0
 #define CREG_BOOT_WP_OFFSET	8