On R-Car H1 and Gen2, the SYSC interrupt registers are always configured
using hardcoded values in platform code. For R-Car Gen2, values are
provided for H2 and M2-W only, other SoCs are not yet supported, and
never will be.

Move this configuration from SoC-specific platform code to the
rcar_sysc_init() wrapper, so it can be skipped if the SYSC is configured
from DT. This would be the case not only for H1, H2, and M2-W using a
modern DTS, but also for other R-Car Gen2 SoCs not supported by the
platform code, relying purely on DT.

There is no longer a need to return the mapped register block, hence
make the function return void.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulrich Hecht <ulrich.hecht+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>