platform/chrome: cros_ec_spi: Document missing function parameters

Kerneldoc expects all kernel function members to be documented.

Fixes the following W=1 level warnings:

  cros_ec_spi.c:153: warning: Function parameter or member 'ec_dev' not described in 'receive_n_bytes'
  cros_ec_spi.c:153: warning: Function parameter or member 'buf' not described in 'receive_n_bytes'
  cros_ec_spi.c:153: warning: Function parameter or member 'n' not described in 'receive_n_bytes'
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>

drivers/platform/chrome/cros_ec_spi.c

@@ -148,6 +148,10 @@ static int terminate_request(struct cros_ec_device *ec_dev)
  * receive_n_bytes - receive n bytes from the EC.
  *
  * Assumes buf is a pointer into the ec_dev->din buffer
+ *
+ * @ec_dev: ChromeOS EC device.
+ * @buf: Pointer to the buffer receiving the data.
+ * @n: Number of bytes received.
  */
 static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
 {