ARM: rmobile: Convert CONFIG_R8A77xx to Kconfig

Convert these configuration options to Kconfig, update board defconfigs
and drop them from whitelist.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/configs/armadillo-800eva_defconfig b/configs/armadillo-800eva_defconfig
index 14d6c84..cade19e 100644
--- a/configs/armadillo-800eva_defconfig
+++ b/configs/armadillo-800eva_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 # CONFIG_SYS_THUMB_BUILD is not set
 CONFIG_ARCH_RMOBILE=y
+CONFIG_R8A7740=y
 CONFIG_TARGET_ARMADILLO_800EVA=y
 CONFIG_BOOTDELAY=3
 CONFIG_VERSION_VARIABLE=y