net: stmmac: reduce dma ring display code duplication

The code to show extended descriptor is identical to normal one.
Consolidate the code to remove duplication.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Link: https://lore.kernel.org/r/a2a5c5ce9338bdea60ec71d7eeb00fe757281557.1700372381.git.baruch@tkos.co.il


Signed-off-by: Paolo Abeni <pabeni@redhat.com>