riscv: add run mode configuration for SPL

U-Boot SPL can be run in a different privilege mode from U-Boot proper.
Add new configuration entries for SPL to allow the run mode to be
configured independently of U-Boot proper.

Extend all uses of the CONFIG_RISCV_SMODE and CONFIG_RISCV_MMODE
configuration symbols to also cover the SPL equivalents. Ensure that
files compatible with only one privilege mode are not included in builds
targeting an incompatible privilege mode.

Signed-off-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index e06db40..e82ee9e 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -39,7 +39,7 @@
 .section .text
 .globl _start
 _start:
-#ifdef CONFIG_RISCV_MMODE
+#if CONFIG_IS_ENABLED(RISCV_MMODE)
 	csrr	a0, CSR_MHARTID
 #endif
 
@@ -62,7 +62,7 @@
 
 #ifdef CONFIG_SMP
 	/* set xSIE bit to receive IPIs */
-#ifdef CONFIG_RISCV_MMODE
+#if CONFIG_IS_ENABLED(RISCV_MMODE)
 	li	t0, MIE_MSIE
 #else
 	li	t0, SIE_SSIE
@@ -344,7 +344,7 @@
 
 #ifdef CONFIG_SMP
 	csrr	t0, MODE_PREFIX(ip)
-#ifdef CONFIG_RISCV_MMODE
+#if CONFIG_IS_ENABLED(RISCV_MMODE)
 	andi	t0, t0, MIE_MSIE
 #else
 	andi	t0, t0, SIE_SSIE