mmc: loongson2: Fix sg iteration in data reorder functions
In ls2k0500_mmc_reorder_cmd_data() and ls2k2000_mmc_reorder_cmd_data(),
the for_each_sg() macro already iterates over the scatterlist entries,
with 'sg' pointing to the current entry. However, the code incorrectly
uses '&sg[i]' and 'sg_dma_len(&sg[i])' inside the loop, which treats
'sg' as an array base and indexes it again, leading to access of
wrong sg entries (or out-of-bounds if the list is not an array).