misc: Kconfig: Make MCHP_LAN966X_PCI depend on OF_OVERLAY

Drivers should depend on configurations that can be user-configurable
instead of selecting them.

Without this patch, OF cannot be disabled this way:
make allyesconfig
scripts/config -d OF
make olddefconfig

Which is a typical test in CI systems like media-ci.

Now that we are at it, remove the dependency on OF, it will come
automatically from OF_OVERLAY.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://lore.kernel.org/r/20241129-lan966x-depend-v2-1-72bb9397f421@chromium.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>