kconfig: use a menu in arch/Kconfig to reduce clutter

Put everything in arch/Kconfig into a General options menu
so that they don't clutter up the main/major/primary list of
menu options.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>