MAINTAINERS: Orphan HSR network protocol

The current maintainer Arvid Brodin <arvid.brodin@alten.se> hasn't
contributed to the kernel since 2015-02-27. His company mail address is
also bouncing and the company confirmed (2020-01-31) that no Arvid Brodin
is working for them:

> Vi har dessvärre ingen  Arvid Brodin som arbetar på ALTEN.

A MIA person cannot be the maintainer. It is better to mark is as orphaned
until some other person can jump in and take over the responsibility for
HSR.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>