kconfig: rename the defconfig and olddefconfig targets

What 'defconfig' really does is save the current .config to a defconfig,
so it is better named 'savedefconfig' (as other projects do).

What 'olddefconfig' really does is create a .config from a defconfig,
so rename it to 'defconfig' (as other projects do, too).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

# Compute AVR32-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}"

    # gcc ./configure flags

    CT_ARCH_WITH_ARCH=

    CT_ARCH_WITH_ABI=

    CT_ARCH_WITH_CPU=

    CT_ARCH_WITH_TUNE=

    CT_ARCH_WITH_FPU=

    CT_ARCH_WITH_FLOAT=

    CT_TARGET_SYS=none

}