drivers/mmc/tegra2_mmc.c: fix GCC 4.6 warning

Fix:
tegra2_mmc.c: In function 'mmc_send_cmd':
tegra2_mmc.c:230:3: warning: 'mask' may be used uninitialized in this
function [-Wuninitialized]

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Tom Warren <twarren@nvidia.com>

drivers/mmc/tegra2_mmc.c

@@ -162,7 +162,7 @@ static int mmc_send_cmd(struct mmc *mmc, struct mmc_cmd *cmd,
 	struct mmc_host *host = (struct mmc_host *)mmc->priv;
 	int flags, i;
 	int result;
-	unsigned int mask;
+	unsigned int mask = 0;
 	unsigned int retry = 0x100000;
 	debug(" mmc_send_cmd called\n");