sched/signal: add spinlock to g_sigfreeaction

[GUIDINGLI]

Summary

sched/signal: add spinlock to g_sigfreeaction

To avoid nxsig_alloc_action() & nxsig_release_action() competition

Impact

sig_action

Testing

[Ouss4]

@xiaoxiang781216 @GUIDINGLI How about using a private lock here instead of the global one? cc @masayuki2009

[masayuki2009]

@xiaoxiang781216 @GUIDINGLI How about using a private lock here instead of the global one? cc @masayuki2009

Though I think we should use a private lock as much as possible, let me check this PR with spresense.

[xiaoxiang781216]

@masayuki2009 do you have any progress?

[masayuki2009]

@masayuki2009 do you have any progress?

I confirmed this PR works with spresense SMP configurations.
But I prefer to use a private spinlock instead of the global one to improve performance.

[masayuki2009]

I confirmed this PR works with spresense SMP configurations.
But I prefer to use a private spinlock instead of the global one to improve performance.

Let me merge this PR so that I can create a new PR for it.