hexagon: fix IM2COL patch-embed DMA ring overflow The exact-tiling (stride == kernel, no pad/dilation) IM2COL DMA kernel issues IC KH DDR->VTCM descriptors per output row without checking the return value of dma_queue_push(), and then pops IC KH times. The per-thread DMA ring holds 256 entries and a push into a full ring returns false and drops the transfer, so for IC*KH > 255 the remaining rows of the VTCM staging buffer were never written and stale data (often NaN/inf) leaked into the output.