MAINTAINERS: Add indirect_call_wrapper.h to NETWORKING [GENERAL]

indirect_call_wrapper.h  is not, strictly speaking, networking specific.
However, it's git history indicates that in practice changes go through
netdev and thus the netdev maintainers have effectively been taking
responsibility for it.

Formalise this by adding it to the NETWORKING [GENERAL] section in the
MAINTAINERS file.

It is not clear how many other files under include/linux fall into this
category and it would be interesting, as a follow-up, to audit that and
propose further updates to the MAINTAINERS file as appropriate.

Link: https://lore.kernel.org/netdev/20231116010310.4664dd38@kernel.org/Signed-off-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20231120-indirect_call_wrapper-maintainer-v1-1-0a6bb1f7363e@kernel.orgSigned-off-by: Paolo Abeni <pabeni@redhat.com>

MAINTAINERS

@@ -15057,6 +15057,7 @@ F:	Documentation/networking/
 F:	Documentation/process/maintainer-netdev.rst
 F:	Documentation/userspace-api/netlink/
 F:	include/linux/in.h
+F:	include/linux/indirect_call_wrapper.h
 F:	include/linux/net.h
 F:	include/linux/netdevice.h
 F:	include/net/