binutils/doc: Remove '.info' suffix in @ref, etc

binutils/doc: Remove '.info' suffix in @ref, etc

Texinfo 7.2 began showing warnings like:

    binutils.texi:882: warning: do not set .info suffix in reference for manual `ld.info'
    binutils.texi:1365: warning: do not set .info suffix in reference for manual `ld.info'

The Texinfo developers plan to stop removing the '.info' suffix
internally in a future release so without this patch the references will
break in the future.

Signed-off-by: Collin Funk <collin.funk1@gmail.com>