Remove perm_ok argument from sshkey_load_private_type

[jitendrasharma1989]

Remove perm_ok, which could potentially be used to check
for private identification file permissions.
But as sshkey_load_private_type would return
SSH_ERR_KEY_BAD_PERMISSIONS for bad permission.
Hence perm_ok seems redundant.

[jitendrasharma1989]

@djmdjm , @daztucker could you please help in reviewing this patch.
The idea of this patch came from TODO list, which says to fix XXX comments.

I have submitted this patch in openssh-unix-dev mailing list also.
In continuation to this patch i have also submitted another patch in mailing list.(I have not yet created Pull request for that another patch.)