CVE-2026-98492: net: macb: fix dma_alloc_coherent() leak on macb_alloc() error paths

In the Linux kernel, the following vulnerability has been resolved:

net: macb: fix dmaalloccoherent() leak on macballoc() error paths

Fix 3 leaks in macballoc() error paths: - Tx buffer allocated but crossing a 4G boundary: Tx leaked. - Rx buffer allocation fails: Tx leaked. - Rx buffer allocated but crossing a 4G boundary: Tx & Rx leaked.

This is because our error handling calls macbfree(bp) which in turn frees the buffers stored in bp->queues[0], but nothing has been stored in there. Fix by storing allocated buffers into bp->queues[0] ASAP.