crypto: atmel-ecc - Struct headers need to start with keyword 'struct'

Fixes the following W=1 kernel build warning(s):

 drivers/crypto/atmel-ecc.c:41: warning: cannot understand function prototype: 'struct atmel_ecdh_ctx '

Cc: Tudor Ambarus <tudor.ambarus@microchip.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/atmel-ecc.c

@@ -26,7 +26,7 @@
 static struct atmel_ecc_driver_data driver_data;
 
 /**
- * atmel_ecdh_ctx - transformation context
+ * struct atmel_ecdh_ctx - transformation context
  * @client     : pointer to i2c client device
  * @fallback   : used for unsupported curves or when user wants to use its own
  *               private key.