net: ethernet: mtk_eth_soc: fix memory corruption during fq dma init

The loop responsible for allocating up to MTK_FQ_DMA_LENGTH buffers must
only touch as many descriptors, otherwise it ends up corrupting unrelated
memory. Fix the loop iteration count accordingly.

Fixes: c57e5581 ("net: ethernet: mtk_eth_soc: handle dma buffer size soc specific")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241015081755.31060-1-nbd@nbd.name


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