kconfig: remove useless 'default n'

kconfig bools are disabled by default, so specifying 'default n' is useless and
noisy. This patch removes all occurrences of 'default n'.

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

# Compute sparc-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

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

        CT_TARGET_ARCH="${CT_ARCH}64"

    fi

}