linuxkpi: Add mising functions in <linux/kmsg_dump.h>

The DRM generic code started to use `kmsg_dump_get_buffer()` and
`kmsg_dump_rewind()` in Linux 6.11.

Reviewed by:	bz, emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55732

sys/compat/linuxkpi/common/include/linux/kmsg_dump.h

@@ -25,6 +25,11 @@ enum kmsg_dump_reason {
 	KMSG_DUMP_MAX
 };
 
+struct kmsg_dump_iter {
+	uint64_t	cur_seq;
+	uint64_t	next_seq;
+};
+
 struct kmsg_dumper {
 	struct list_head list;
 	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
@@ -32,6 +37,36 @@ struct kmsg_dumper {
 	bool registered;
 };
 
+static inline void
+kmsg_dump(enum kmsg_dump_reason reason)
+{
+	pr_debug("TODO");
+}
+
+static inline bool
+kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
+    const char *line, size_t size, size_t *len)
+{
+	pr_debug("TODO");
+
+	return (false);
+}
+
+static inline bool
+kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog,
+    char *buf, size_t size, size_t *len)
+{
+	pr_debug("TODO");
+
+	return (false);
+}
+
+static inline void
+kmsg_dump_rewind(struct kmsg_dump_iter *iter)
+{
+	pr_debug("TODO");
+}
+
 static inline int
 kmsg_dump_register(struct kmsg_dumper *dumper)
 {
@@ -48,4 +83,11 @@ kmsg_dump_unregister(struct kmsg_dumper *dumper)
 	return (-EINVAL);
 }
 
+static inline const char *
+kmsg_dump_reason_str(enum kmsg_dump_reason reason)
+{
+	pr_debug("TODO");
+
+	return ("Unknown");
+}
 #endif