Add a configuration option for the R-Car D3 SoC.

Note that r8a77995 is the first Renesas "r8a<n>" SoC using a 5 digit
number in its Kconfig symbol, as r8a77990 will be a different SoC.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>