riscv: Introduce a new config for SBI v0.1

We now have SBI v0.2 which is more scalable and extendable to handle
future needs for RISC-V supervisor interfaces.

Introduce a new config and move all SBI v0.1 code under that config.
This allows to implement the new replacement SBI extensions cleanly
and remove v0.1 extensions easily in future. Currently, the config
is enabled by default. Once all M-mode software, with v0.1, is no
longer in use, this config option and all relevant code can be easily
removed.

This commit is inspired from Linux kernel patch:
https://patchwork.kernel.org/patch/11407361/

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>
diff --git a/arch/riscv/lib/sbi.c b/arch/riscv/lib/sbi.c
index 4b6a9e0..604a3a8 100644
--- a/arch/riscv/lib/sbi.c
+++ b/arch/riscv/lib/sbi.c
@@ -39,6 +39,8 @@
 	return ret;
 }
 
+#ifdef CONFIG_SBI_V01
+
 /**
  * sbi_console_putchar() - Writes given character to the console device.
  * @ch: The data to be written to the console.
@@ -84,6 +86,8 @@
 	sbi_ecall(SBI_EXT_0_1_SHUTDOWN, 0, 0, 0, 0, 0, 0, 0);
 }
 
+#endif /* CONFIG_SBI_V01 */
+
 /**
  * sbi_set_timer() - Program the timer for next timer event.
  * @stime_value: The value after which next timer event should fire.