x86: use for_each_clear_bit_from()

Use for_each_clear_bit() to iterate over all the cleared bit in a
memory region.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/irqinit.c

@@ -306,10 +306,10 @@ void __init native_init_IRQ(void)
 	 * us. (some of these will be overridden and become
 	 * 'special' SMP interrupts)
 	 */
-	for (i = FIRST_EXTERNAL_VECTOR; i < NR_VECTORS; i++) {
+	i = FIRST_EXTERNAL_VECTOR;
+	for_each_clear_bit_from(i, used_vectors, NR_VECTORS) {
 		/* IA32_SYSCALL_VECTOR could be used in trap_init already. */
-		if (!test_bit(i, used_vectors))
-			set_intr_gate(i, interrupt[i-FIRST_EXTERNAL_VECTOR]);
+		set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
 	}
 
 	if (!acpi_ioapic && !of_ioapic)