net: airoha: Add NULL check for of_reserved_mem_lookup() in airoha_qdma_init_hfwd_queues()

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

net: airoha: Add NULL check for of_reserved_mem_lookup() in airoha_qdma_init_hfwd_queues()

of_reserved_mem_lookup() may return NULL if the reserved memory region

referenced by the "memory-region" phandle is not found in the reserved

memory table (e.g. due to a misconfigured DTS or a removed

memory-region node). The current code dereferences the returned

pointer without checking for NULL, leading to a kernel NULL pointer

dereference at the following lines:

dma_addr = rmem->base; // line 1156

num_desc = div_u64(rmem->size, buf_size); // line 1160

Add a NULL check after of_reserved_mem_lookup() and return -ENODEV if

the lookup fails, which is consistent with the existing error handling

for of_parse_phandle() failure in the same code block.