kbuild: fix up printing of Linux C Library version in scripts/ver_linux

I noticed, when running scripts/ver_linux on both a Gentoo system
and a Slackware system, that the line printing the C library
version looked a little odd. So I fixed it up to be in line with
all the rest.

  Old output:
    Linux C Library        > libc.2.5
  New output:
    Linux C Library        2.5

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>