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>

CT_LOCAL_TARBALLS_DIR="${HOME}/src"

CT_SAVE_TARBALLS=y

CT_LOG_EXTRA=y

CT_ARCH_LE=y

CT_ARCH_FLOAT_SW=y

CT_ARCH_mips=y

CT_TARGET_VENDOR="sde"

CT_BINUTILS_V_2_21_1a=y

CT_CC_V_4_4_6=y

# CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set

CT_LIBC_none=y

CT_DEBUG_gdb=y

CT_GDB_V_6_8a=y

CT_GMP_V_4_3_2=y

CT_MPFR_V_2_4_2=y

CT_PPL_V_0_10_2=y

CT_CLOOG_V_0_15_10=y