staging: goldfish: document spinlock usage

Coding style: document spinlock usage
Signed-off-by: Loic Pefferkorn <loic@loicp.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/goldfish/goldfish_audio.c

@@ -36,6 +36,7 @@ MODULE_VERSION("1.0");
 struct goldfish_audio {
 	char __iomem *reg_base;
 	int irq;
+	/* lock protects access to buffer_status and to device registers */
 	spinlock_t lock;
 	wait_queue_head_t wait;