Use jr as register jump instruction

Current assembler codes are inconsistent in the way of register jump
instruction usage; some use jr, some use j. Of course GNU as allows both
usages, but as can be expected from `Jump Register' the mnemonic `jr' is
more intuitive than `j'. For example, Linux doesn't have `j <reg>' usage
at all.

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
diff --git a/board/qemu-mips/lowlevel_init.S b/board/qemu-mips/lowlevel_init.S
index 28166bc..836e027 100644
--- a/board/qemu-mips/lowlevel_init.S
+++ b/board/qemu-mips/lowlevel_init.S
@@ -37,5 +37,5 @@
 	mtc0	zero, CP0_WIRED
 	nop
 
-	j	ra
+	jr	ra
 	nop