net: dwc_eth_qos: cosmetic: remove unused define EQOS_DESCRIPTOR_ALIGN

Remove the define EQOS_DESCRIPTOR_ALIGN unused since the
commit 6f1e668d ("net: dwc_eth_qos: Pad descriptors to cacheline size")

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>