riscv: Introduce CONFIG_XIP to support booting from flash

When U-Boot boots from flash, during the boot process,
hart_lottery and available_harts_lock variable addresses
point to flash which is not writable. This causes boot
failures on AE350. Introduce a config option CONFIG_XIP
to support such configuration.

Signed-off-by: Rick Chen <rick@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Reviewed-by: Lukas Auer <lukas.auer@aisec.fraunhofer.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/riscv/lib/smp.c b/arch/riscv/lib/smp.c
index caa292c..cc66f15 100644
--- a/arch/riscv/lib/smp.c
+++ b/arch/riscv/lib/smp.c
@@ -63,9 +63,11 @@
 			continue;
 		}
 
+#ifndef CONFIG_XIP
 		/* skip if hart is not available */
 		if (!(gd->arch.available_harts & (1 << reg)))
 			continue;
+#endif
 
 		gd->arch.ipi[reg].addr = ipi->addr;
 		gd->arch.ipi[reg].arg0 = ipi->arg0;