blktrace: use BLKTRACE_BDEV_SIZE as the name size for setup structure

Define as 32, which is is what BDEVNAME_SIZE is/was as well. This keeps
the user interface the same and gets rid of the difference between
kernel and user api here.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blktrace.c b/block/blktrace.c
index 9e0212c..85049a7 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -369,7 +369,8 @@
 	if (!buts->buf_size || !buts->buf_nr)
 		return -EINVAL;
 
-	strcpy(buts->name, name);
+	strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
+	buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
 
 	/*
 	 * some device names have larger paths - convert the slashes