configs: ax25-ae350: Set 64-bit as default configuration

Set 64-bit as default configuration for ax25-ae350.

Signed-off-by: Rick Chen <rick@andestech.com>
Signed-off-by: Rick Chen <rickchen36@gmail.com>
Cc: Greentime Hu <green.hu@gmail.com>
diff --git a/configs/ax25-ae350_defconfig b/configs/ax25-ae350_defconfig
index 45a36e6..002f170 100644
--- a/configs/ax25-ae350_defconfig
+++ b/configs/ax25-ae350_defconfig
@@ -39,3 +39,4 @@
 CONFIG_TIMER=y
 CONFIG_ATCPIT100_TIMER=y
 CONFIG_DISTRO_DEFAULTS=y
+CONFIG_CPU_RISCV_64=y