staging/lustre/libcfs: cleanup libcfs_kkuc_msg_put a bit

No need to cast count since it is already ssize_t. No need
to cast payload to const, but need __force instead to avoid
Sparse complaining.
Reported-and-Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>
Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/libcfs/kernel_user_comm.c

@@ -170,8 +170,8 @@ int libcfs_kkuc_msg_put(struct file *filp, void *payload)
 
 	fs = get_fs();
 	set_fs(KERNEL_DS);
-	while ((ssize_t)count > 0) {
-		rc = vfs_write(filp, (const void __user *)payload,
+	while (count > 0) {
+		rc = vfs_write(filp, (void __force __user *)payload,
 			       count, &offset);
 		if (rc < 0)
 			break;