riscv: Avoid updating the link register

board_init_r does not return for U-Boot SPL hence there is no need
to update the link register when jumping to board_init_r.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/cpu/start.S b/arch/riscv/cpu/start.S
index c09d1cb..8cf25bb 100644
--- a/arch/riscv/cpu/start.S
+++ b/arch/riscv/cpu/start.S
@@ -250,7 +250,7 @@
 spl_call_board_init_r:
 	mv	a0, zero
 	mv	a1, zero
-	jal	board_init_r
+	j	board_init_r
 #endif
 
 /*