kconfig: add CONFIG_SYS_{ARCH, CPU, ...} type def to arch/Kconfig

This commit adds the type definitions (+ help messages) of
CONFIG_SYS_{ARCH, CPU, SOC, VENDOR, BOARD, CONFIG_NAME} to arch/Kconfig,
which would save lots of type defs for taget boards.
(See also the next commit.)

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>