hsr: fix dummy hsr_debugfs_rename() declaration

The hsr_debugfs_rename prototype got an extra 'void' that needs to
be removed again:

In file included from /git/arm-soc/net/hsr/hsr_main.c:12:
net/hsr/hsr_main.h:194:20: error: two or more data types in declaration specifiers
 static inline void void hsr_debugfs_rename(struct net_device *dev)

Fixes: 4c2d5e33 ("hsr: rename debugfs file when interface name is changed")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>