csky: Fixup kprobes handler couldn't change pc

The "Changing Execution Path" section in the Documentation/kprobes.txt
said:

Since kprobes can probe into a running kernel code, it can change the
register set, including instruction pointer.
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>

arch/csky/abiv2/mcount.S

@@ -55,7 +55,9 @@
 
 .macro mcount_exit_regs
 	RESTORE_REGS_FTRACE
-	ldw	t1, (sp, 0)
+	subi	sp, 152
+	ldw	t1, (sp, 4)
+	addi	sp, 152
 	ldw	r8, (sp, 4)
 	ldw	lr, (sp, 8)
 	addi	sp, 12