MAINTAINERS: switch maintainer of the hso driver

Since Denis is no longer working for Option, I will maintain the driver from
now on.

Signed-off-by: Jan Dumon <j.dumon@option.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>