Enable -O3 Kernel Code Optimizations + Fixes!

net/ipv4/tcp_input.c: In function âp_data_queueânet/ipv4/tcp_input.c:4417:49: warning: array subscript is above array bounds [-Warray-bounds]
     tp->selective_acks[i-1] = tp->selective_acks[i];

drivers/md/bcache/bset.c: In function âh_btree_sort_partialâdrivers/md/bcache/bset.c:1076:19: warning: array subscript is above array bounds [-Warray-bounds]
    keys += b->sets[i].data->keys;