MAINTAINERS: update kdump maintainers

Remove myself from kdump maintainers as I have no enough time to maintain
it now.  But I can review patches on demand though.

Link: https://lkml.kernel.org/r/YZyKilzKFsWJYdgn@dhcp-128-65.nay.redhat.comSigned-off-by: Dave Young <dyoung@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -10279,9 +10279,9 @@ F:	lib/Kconfig.kcsan
 F:	scripts/Makefile.kcsan
 
 KDUMP
-M:	Dave Young <dyoung@redhat.com>
 M:	Baoquan He <bhe@redhat.com>
 R:	Vivek Goyal <vgoyal@redhat.com>
+R:	Dave Young <dyoung@redhat.com>
 L:	kexec@lists.infradead.org
 S:	Maintained
 W:	http://lse.sourceforge.net/kdump/