net: fec: add pagepool_order to support variable page size

Add a new pagepool_order member in the fec_enet_private struct
to allow dynamic configuration of page size for an instance. This
change clears the hardcoded page size assumptions.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Wei Fang <wei.fang@nxp.com>
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Link: https://patch.msgid.link/20250910185211.721341-3-shenwei.wang@nxp.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>