binutils/binutils: fix extra config array variable name

The changeset 2467 #200836977ce6 missed renaming one occurrence of
CT_BINUTILS_EXTRA_CONFIG to CT_BINUTILS_EXTRA_CONFIG_ARRAY, which is fixed by
this patch.

Signed-off-by: "Benoît Thébaudeau" <benoit.thebaudeau@advansee.com>

 # Compute s390-specific values

 CT_DoArchTupleValues() {

     # That's the only thing to override

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

         CT_TARGET_ARCH="s390x"

     fi

 }