config: move kernel configuration to independent file

Move to kernel/Kconfig

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
config: centralize development configuration

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
config: move options to config system

Move DEBUG, CONFIG_DEBUG, CONFIG_KDB to kernel/Kconfig

Signed-off-by: Viller Hsiao <villerhsiao@gmail.com>
Merge remote-tracking branch 'vh21/tweak-dbg'
mk: minor comment update