net: dsa: lantiq: Fix path in MAINTAINERS file

The MAINTAINERS file contained the wrong file name of the driver.

Fixes: 14fceff4 ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>