minor fix to smp(4) man page

[Gabor Kovesdan]

On 2011.09.23. 0:05, Alexander Best wrote:
> hi there,
>
> could somebody please commit the following fix?
>
Thanks for your patch! I just submitted it to re@ for approval. Note, 
that we do not bump .Dd for such changes, just for real content change. 
Also, you had a dot instead of a comma in the reference list, which I 
fixed in my working copy. :)

Gabor