riscv: Do not return error if reserved node already exists

Not all errors are fatal. If a reserved memory node already exists in the
destination device tree, we can continue to boot without failing.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
diff --git a/arch/riscv/lib/fdt_fixup.c b/arch/riscv/lib/fdt_fixup.c
index 160ccca..bd4a3c9 100644
--- a/arch/riscv/lib/fdt_fixup.c
+++ b/arch/riscv/lib/fdt_fixup.c
@@ -74,7 +74,7 @@
 		pmp_mem.end = addr + size - 1;
 		err = fdtdec_add_reserved_memory(dst, basename, &pmp_mem,
 						 &phandle);
-		if (err < 0) {
+		if (err < 0 && err != -FDT_ERR_EXISTS) {
 			printf("failed to add reserved memory: %d\n", err);
 			return err;
 		}