MAINTAINERS: Orphan HSR network protocol

The current maintainer Arvid Brodin <[e-mail]> 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 <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

MAINTAINERS

···
 F:	drivers/net/usb/hso.c
 
 HSR NETWORK PROTOCOL
-M:	Arvid Brodin <[e-mail]>
 L:	[e-mail]
-S:	Maintained
+S:	Orphan
 F:	net/hsr/
 
 HT16K33 LED CONTROLLER DRIVER