MAINTAINERS: Add include/linux/tnum.h to BPF CORE

Maintainers of the kerne/bpf/tnum.c are also the maintainers of the
corresponding header file include/linux/tnum.h.

Add the file entry for include/linux/tnum.h to the appropriate section
in MAINTAINERS.

Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220831034039.17998-1-shung-hsi.yu@suse.com

MAINTAINERS

@@ -3824,6 +3824,7 @@ F:	kernel/bpf/dispatcher.c
 F:	kernel/bpf/trampoline.c
 F:	include/linux/bpf*
 F:	include/linux/filter.h
+F:	include/linux/tnum.h
 
 BPF [BTF]
 M:	Martin KaFai Lau <martin.lau@linux.dev>