ARM: shmobile: Cleanup pm-rcar.o build using Kconfig

Add a CONFIG_PM_RCAR entry and enable it for R-Car
Generation 1 or 2 in case CONFIG_PM or CONFIG_SMP
is set. Consolidate power management objects and
get rid of #ifdefs in the C code.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>