misc: bcm-vk: Replace zero-length array with flexible array member

There is a regular need in the kernel to provide a way to declare
having a dynamically sized set of trailing elements in a structure.
Kernel code should always use “flexible array members”[1] for these
cases. The older style of one-element or zero-length arrays should
no longer be used[2].

Also, make use of the struct_size() helper in kzalloc().

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arraysAcked-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20210514230801.GA35863@embeddedorSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/bcm-vk/bcm_vk_msg.c

@@ -701,8 +701,7 @@ int bcm_vk_send_shutdown_msg(struct bcm_vk *vk, u32 shut_type,
 		return -EINVAL;
 	}
 
-	entry = kzalloc(sizeof(*entry) +
-			sizeof(struct vk_msg_blk), GFP_KERNEL);
+	entry = kzalloc(struct_size(entry, to_v_msg, 1), GFP_KERNEL);
 	if (!entry)
 		return -ENOMEM;
 

drivers/misc/bcm-vk/bcm_vk_msg.h

@@ -116,7 +116,7 @@ struct bcm_vk_wkent {
 	u32 usr_msg_id;
 	u32 to_v_blks;
 	u32 seq_num;
-	struct vk_msg_blk to_v_msg[0];
+	struct vk_msg_blk to_v_msg[];
 };
 
 /* queue stats counters */