[texdoc] lm -> lm, not cfr-lm

[Karl Berry]

Hi Manuel,

$ texdoc -l lm
 1 /home/texlive/karl/Master/texmf-dist/doc/fonts/cfr-lm/cfr-lm.pdf
   = Package documentation
 2 /home/texlive/karl/Master/texmf-dist/doc/fonts/lm/lm-info.pdf
..

It would be better for lm to return the first entry in the lm package
rather than anything from another package (regardless of whether it has
Catalogue commentary).  Does texdoc have the concept of package?

Thanks,
k