arm64: renesas: Align configuration headers

arm64: renesas: Align configuration headers

Align R-Car Gen2/Gen3/Gen4 configuration header file to look
basically the same way across these three SoC generations.
There are subtle difference between the remaining bits in
those files across SoC generations, but the common bits are
now aligned. There is not much left in those headers either,
most of the configuration is now converted to Kconfig.

Specifically for R-Car Gen3, GIC registers have been moved
to architecture specific header file rcar-gen3-base.h , the
rest of the changes here are comment changes and indentation
changes.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>