MAINTAINERS: repair reference in LYNX PCS MODULE

Commit 0da4c3d3 ("net: phy: add Lynx PCS module") added the files in
./drivers/net/pcs/, but the new LYNX PCS MODULE section refers to
./drivers/net/phy/.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches    F:    drivers/net/phy/pcs-lynx.c

Repair the LYNX PCS MODULE section by referring to the right location.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>