mailbox: hi3660: convert struct comments to kernel-doc notation

Convert hi3660 struct comments to kernel-doc notation and fix
other kernel-doc warnings:

drivers/mailbox/hi3660-mailbox.c:47: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Hi3660 mailbox channel information
drivers/mailbox/hi3660-mailbox.c:62: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Hi3660 mailbox controller data
hi3660-mailbox.c:53: warning: contents before sections
hi3660-mailbox.c:67: warning: contents before sections

Fixes: 41c0e939 ("mailbox: Add support for Hi3660 mailbox")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Ruyi Wang <wangruyi@huawei.com>
Cc: Kaihua Zhong <zhongkaihua@huawei.com>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/hi3660-mailbox.c

@@ -44,14 +44,13 @@
 #define MBOX_MSG_LEN			8
 
 /**
- * Hi3660 mailbox channel information
+ * struct hi3660_chan_info - Hi3660 mailbox channel information
+ * @dst_irq:	Interrupt vector for remote processor
+ * @ack_irq:	Interrupt vector for local processor
  *
  * A channel can be used for TX or RX, it can trigger remote
  * processor interrupt to notify remote processor and can receive
- * interrupt if has incoming message.
- *
- * @dst_irq:	Interrupt vector for remote processor
- * @ack_irq:	Interrupt vector for local processor
+ * interrupt if it has an incoming message.
  */
 struct hi3660_chan_info {
 	unsigned int dst_irq;
@@ -59,16 +58,15 @@ struct hi3660_chan_info {
 };
 
 /**
- * Hi3660 mailbox controller data
- *
- * Mailbox controller includes 32 channels and can allocate
- * channel for message transferring.
- *
+ * struct hi3660_mbox - Hi3660 mailbox controller data
  * @dev:	Device to which it is attached
  * @base:	Base address of the register mapping region
  * @chan:	Representation of channels in mailbox controller
  * @mchan:	Representation of channel info
  * @controller:	Representation of a communication channel controller
+ *
+ * Mailbox controller includes 32 channels and can allocate
+ * channel for message transferring.
  */
 struct hi3660_mbox {
 	struct device *dev;