bpf: Add schedule points in batch ops

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

bpf: Add schedule points in batch ops

syzbot reported various soft lockups caused by bpf batch operations.

INFO: task kworker/1:1:27 blocked for more than 140 seconds.

INFO: task hung in rcu_barrier

Nothing prevents batch ops to process huge amount of data,

we need to add schedule points in them.

Note that maybe_wait_bpf_programs(map) calls from

generic_map_delete_batch() can be factorized by moving

the call after the loop.

This will be done later in -next tree once we get this fix merged,

unless there is strong opinion doing this optimization sooner.