i2c: fix spelling mistake: "insufficent" -> "insufficient"

Trivial fix to spelling mistake in WARN message, insufficient has
an insufficient number of i's in the spelling.
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core.c

@@ -3632,7 +3632,7 @@ int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 	int ret;
 
 	if (!client || !slave_cb) {
-		WARN(1, "insufficent data\n");
+		WARN(1, "insufficient data\n");
 		return -EINVAL;
 	}