complibs: remove experimental from versions selection

Since I removed EXPERIMENTAL to most of gcc versions, the configuration
is now broken, as the required companion libraries versions are not
selectable, as they are still hidden behind EXPERIMENTAL.

Reported-by: Claudio Henrique Fortes Felix (chffelix on irc://irc.freenode.net/crosstool-ng)
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

# Compute s390-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

    if [ "${CT_ARCH_64}" = "y" ]; then

        CT_TARGET_ARCH="s390x"

    fi

}