MAINTAINERS: Adjust entry in XDP SOCKETS to actual file name

Commit 2b43470a ("xsk: Introduce AF_XDP buffer allocation API") added a
new header file include/net/xsk_buff_pool.h, but commit 28bee21d
("MAINTAINERS, xsk: Update AF_XDP section after moves/adds") added a file
entry referring to include/net/xsk_buffer_pool.h.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches  F:  include/net/xsk_buffer_pool.h

Adjust the entry in XDP SOCKETS to the actual file name.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200525141553.7035-1-lukas.bulwahn@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

MAINTAINERS

@@ -18456,7 +18456,7 @@ L:	netdev@vger.kernel.org
 L:	bpf@vger.kernel.org
 S:	Maintained
 F:	include/net/xdp_sock*
-F:	include/net/xsk_buffer_pool.h
+F:	include/net/xsk_buff_pool.h
 F:	include/uapi/linux/if_xdp.h
 F:	net/xdp/
 F:	samples/bpf/xdpsock*