arm64: defconfig: enable RTC on Armada 7K/8K SoCs

The Armada 38x RTC driver supports also the RTC controller found on the
Armada 7K/8K SoCs, so enable it.
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm64/configs/defconfig

@@ -472,6 +472,7 @@ CONFIG_RTC_DRV_EFI=y
 CONFIG_RTC_DRV_S3C=y
 CONFIG_RTC_DRV_PL031=y
 CONFIG_RTC_DRV_SUN6I=y
+CONFIG_RTC_DRV_ARMADA38X=y
 CONFIG_RTC_DRV_TEGRA=y
 CONFIG_RTC_DRV_XGENE=y
 CONFIG_DMADEVICES=y