sram_alloc
ring_pa = sram_alloc(nbd * sizeof(uint32_t) * 2, sizeof(uint32_t) * 2);
pa = sram_alloc(bestcomm_image_bytes, BESTCOMM_TASKBAR_ALIGN);
bus_addr_t sram_alloc(size_t, size_t); /* size, alignment -> phys, 0 fail */