arm64: defconfig: Replace ARCH_R8A7796 by ARCH_R8A77960

CONFIG_ARCH_R8A7796 was replaced by CONFIG_ARCH_R8A77960, cfr. commits
39e57e14 ("soc: renesas: Add ARCH_R8A77960 for existing R-Car
M3-W") and 24240845 ("soc: renesas: Remove ARCH_R8A7796").
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200217101741.3758-1-geert+renesas@glider.be

arch/arm64/configs/defconfig

@@ -771,7 +771,7 @@ CONFIG_ARCH_R8A774A1=y
 CONFIG_ARCH_R8A774B1=y
 CONFIG_ARCH_R8A774C0=y
 CONFIG_ARCH_R8A7795=y
-CONFIG_ARCH_R8A7796=y
+CONFIG_ARCH_R8A77960=y
 CONFIG_ARCH_R8A77961=y
 CONFIG_ARCH_R8A77965=y
 CONFIG_ARCH_R8A77970=y