hw/net/cadence_gem: use FIELD to describe NWCTRL register fields

Use the FIELD macro to describe the NWCTRL register fields.

Signed-off-by: Luc Michel <luc.michel@amd.com>
Reviewed-by: sai.pavan.boddu@amd.com
Message-id: 20231017194422.4124691-4-luc.michel@amd.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
1 file changed