MAINTAINERS: update btrfs website links and files

We have the new documentation hosted on Read The Docs and content is
migrated there from the wiki. Also update http to https and add the
tracepoint definition header.

Signed-off-by: David Sterba <[email protected]>

Author: kdave

MAINTAINERS

@@ -4428,13 +4428,15 @@ M:	Josef Bacik <[email protected]>
 M:	David Sterba <[email protected]>
 L:	[email protected]
 S:	Maintained
-W:	http://btrfs.wiki.kernel.org/
-Q:	http://patchwork.kernel.org/project/linux-btrfs/list/
+W:	https://btrfs.readthedocs.io
+W:	https://btrfs.wiki.kernel.org/
+Q:	https://patchwork.kernel.org/project/linux-btrfs/list/
 C:	irc://irc.libera.chat/btrfs
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git
 F:	Documentation/filesystems/btrfs.rst
 F:	fs/btrfs/
 F:	include/linux/btrfs*
+F:	include/trace/events/btrfs.h
 F:	include/uapi/linux/btrfs*
 
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