MAINTAINERS: list PTP drivers under networking

PTP patches go via the netdev trees, add drivers/ptp/ to the networking
entry so that get_maintainer.pl --scm lists those trees above Linus's
tree.

Thanks to the real entry using drivers/ptp/* the original entry will
still be considered more specific / higher prio.

Acked-by: Richard Cochran <richardcochran@gmail.com>
Link: https://patch.msgid.link/20241130214100.125325-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

MAINTAINERS

@@ -16194,6 +16194,7 @@ F:	Documentation/devicetree/bindings/net/
 F:	Documentation/networking/net_cachelines/net_device.rst
 F:	drivers/connector/
 F:	drivers/net/
+F:	drivers/ptp/
 F:	include/dt-bindings/net/
 F:	include/linux/cn_proc.h
 F:	include/linux/etherdevice.h