mmc/dwmmc: Using calloc instead malloc

To enhance the SDMMC DesignWare driver to use calloc instead of
malloc. This will avoid the incident that uninitialized members
of mmc structure are later used for NULL comparison.

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

drivers/mmc/dw_mmc.c

@@ -336,9 +336,9 @@ int add_dwmci(struct dwmci_host *host, u32 max_clk, u32 min_clk)
 	struct mmc *mmc;
 	int err = 0;
 
-	mmc = malloc(sizeof(struct mmc));
+	mmc = calloc(sizeof(struct mmc), 1);
 	if (!mmc) {
-		printf("mmc malloc fail!\n");
+		printf("mmc calloc fail!\n");
 		return -1;
 	}