Documentation: add some docs for errseq_t

...and fix up a few comments in the code.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
diff --git a/include/linux/errseq.h b/include/linux/errseq.h
index 784f086..f746bd8 100644
--- a/include/linux/errseq.h
+++ b/include/linux/errseq.h
@@ -1,8 +1,9 @@
+/*
+ * See Documentation/errseq.rst and lib/errseq.c
+ */
 #ifndef _LINUX_ERRSEQ_H
 #define _LINUX_ERRSEQ_H
 
-/* See lib/errseq.c for more info */
-
 typedef u32	errseq_t;
 
 errseq_t errseq_set(errseq_t *eseq, int err);