ARM: rmobile: Unify Gen2 Makefile entry

Drop per-SoC Makefile entries and replace them with one unified entry
now that the PFC tables are gone. Shuffle the Makefile around a bit
to make it more organized.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>