ARM: shmobile: Add the RZ/N1 arch to the shmobile Kconfig

Add the RZ/N1 Family (Part #R9A06G0xx) ARCH config to the rest of
the Renesas SoC collection.

Signed-off-by: Michel Pollet <michel.pollet@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>