net: ravb: Make DBAT entry count configurable per-SoC

net: ravb: Make DBAT entry count configurable per-SoC

Avoid wasting coherent DMA memory by allocating the descriptor base
address table sized for the actual number of DBAT/CDARq entries supported
by the SoC. Some platforms (for example GBETH) only provide two CDARq
entries; previously the driver always allocated space for 22 entries which
needlessly consumed memory on those systems.

Pass the per-SoC dbat_entry_num via struct ravb_hw_info and use it for
allocation and initialization in probe. This sizes the table correctly and
removes the unnecessary memory overhead on SoCs with fewer DBAT entries.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://patch.msgid.link/20251023112111.215198-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>