x86: kprobes: fix swapped segment registers in kretprobe

In commit f007ea26, the order of the %es and %ds segment registers
got accidentally swapped, so synthesized 'struct pt_regs' frames
have the two values inverted.  It's almost sure that these values
never matter, and that they also never differ.  But wrong is wrong.
Signed-off-by: Roland McGrath <roland@redhat.com>

arch/x86/kernel/kprobes.c

@@ -640,8 +640,8 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 	/* Skip cs, ip, orig_ax and gs. */	\
 	"	subl $16, %esp\n"	\
 	"	pushl %fs\n"		\
-	"	pushl %ds\n"		\
 	"	pushl %es\n"		\
+	"	pushl %ds\n"		\
 	"	pushl %eax\n"		\
 	"	pushl %ebp\n"		\
 	"	pushl %edi\n"		\