docs/125751: man 3 pthread_getschedparam section ERRORS incomplete

[Dan Lukes]

On 02/22/11 22:41, Bruce Cran:
> According to POSIX EINVAL isn't a valid return value

I don't have problem with proposed patch. I reported the issue because I 
got EIVAL and it has not been documented.

Either code or documentation needs to be changed to make them 
consistent, but I don't care what part will be corrected.

Thank you for taking those ancient PRs ...

Dan