i386: fix asm constraint in do_IRQ()

Two prior changes resulted in the "ecx" clobber being lost.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/irq_32.c

@@ -134,7 +134,7 @@ unsigned int do_IRQ(struct pt_regs *regs)
 			: "=a" (arg1), "=d" (arg2), "=b" (bx)
 			:  "0" (irq),   "1" (desc),  "2" (isp),
 			   "D" (desc->handle_irq)
-			: "memory", "cc"
+			: "memory", "cc", "ecx"
 		);
 	} else
 #endif