net: socket: Enable parameter check (addr and addrlen) in getsockname.c

[masayuki2009]

Summary

• This PR reinforces parameter check in getsockname()
• With this fix, an error in BasicGetSockName test in usrsocktest will be fixed.

Impact

• This PR affects network programs which use getsockname()
• However, this is a minor error case, so existing application should work.

Limitations / TODO

• There still remain errors in usrsocktest and need more investigation.

Testing

• I tested this PR with spresense:wifi which I added usrsocktest application.