riscv: Make SBI v0.2 the default SBI version

To work with latest OpenSBI release (v0.7 or above) that has the HSM
extension support, select the SBI v0.2 support by default.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c729871..fb5fe5a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -228,7 +228,7 @@
 
 choice
 	prompt "SBI support"
-	default SBI_V01
+	default SBI_V02
 
 config SBI_V01
 	bool "SBI v0.1 support"