hw/arm/npcm7xx: Call qemu_configure_nic_device() for GMAC modules

hw/arm/npcm7xx: Call qemu_configure_nic_device() for GMAC modules

The patchset adding the GMAC ethernet to this SoC crossed in the
mail with the patchset cleaning up the NIC handling. When we
create the GMAC modules we must call qemu_configure_nic_device()
so that the user has the opportunity to use the -nic commandline
option to create a network backend and connect it to the GMACs.

Add the missing call.

Fixes: 21e5326a7c ("hw/arm: Add GMAC devices to NPCM7XX SoC")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Message-id: 20240206171231.396392-2-peter.maydell@linaro.org