spi/atmel: Annotate lock/unlock functions

Let checkers like sparse know that the locking imbalances are intentional
in these functions.

Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 4c6c455..4e40693 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -360,12 +360,12 @@
 		gpio_set_value(asd->npcs_pin, !active);
 }
 
-static void atmel_spi_lock(struct atmel_spi *as)
+static void atmel_spi_lock(struct atmel_spi *as) __acquires(&as->lock)
 {
 	spin_lock_irqsave(&as->lock, as->flags);
 }
 
-static void atmel_spi_unlock(struct atmel_spi *as)
+static void atmel_spi_unlock(struct atmel_spi *as) __releases(&as->lock)
 {
 	spin_unlock_irqrestore(&as->lock, as->flags);
 }