soc: renesas: Remove ARCH_R8A7795

Replace the final user of CONFIG_ARCH_R8A7795 by CONFIG_ARCH_R8A77950 ||
CONFIG_ARCH_R8A77951, and remove the now unused CONFIG_ARCH_R8A7795
symbol definition.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200218112449.5723-1-geert+renesas@glider.be