MAINTAINERS: add files related to kdump

Kdump is implemented based on kexec, however some files are only related
to crash dumping and missing, add them to KDUMP entry.
Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Dave Young <dyoung@redhat.com>
Link: http://lkml.kernel.org/r/20200520103633.GW5029@MiWiFi-R3L-srvSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -9185,6 +9185,11 @@ L:	kexec@lists.infradead.org
 S:	Maintained
 W:	http://lse.sourceforge.net/kdump/
 F:	Documentation/admin-guide/kdump/
+F:	fs/proc/vmcore.c
+F:	include/linux/crash_core.h
+F:	include/linux/crash_dump.h
+F:	include/uapi/linux/vmcore.h
+F:	kernel/crash_*.c
 
 KEENE FM RADIO TRANSMITTER DRIVER
 M:	Hans Verkuil <hverkuil@xs4all.nl>