In alternative_instructions(), call free_init_pages() with irqs enabled.

It fixes the warning message in smp_call_function*(), which should not be
called with irqs disabled.

[    0.310000] CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line)
[    0.310000] CPU: L2 Cache: 512K (64 bytes/line)
[    0.310000] CPU 0/0 -> Node 0
[    0.310000] SMP alternatives: switching to UP code
[    0.310000] Freeing SMP alternatives: 25k freed
[    0.310000] WARNING: at arch/x86_64/kernel/smp.c:397 smp_call_function_mask()
[    0.310000]
[    0.310000] Call Trace:
[    0.310000]  [<ffffffff8100dbde>] dump_trace+0x3ee/0x4a0
[    0.310000]  [<ffffffff8100dcd3>] show_trace+0x43/0x70
[    0.310000]  [<ffffffff8100dd15>] dump_stack+0x15/0x20
[    0.310000]  [<ffffffff8101cd44>] smp_call_function_mask+0x94/0xa0
[    0.310000]  [<ffffffff8101d0b2>] smp_call_function+0x32/0x40
[    0.310000]  [<ffffffff8104277f>] on_each_cpu+0x1f/0x50
[    0.310000]  [<ffffffff81026eac>] global_flush_tlb+0x8c/0x110
[    0.310000]  [<ffffffff81025c85>] free_init_pages+0xe5/0xf0
[    0.310000]  [<ffffffff81549b5e>] alternative_instructions+0x7e/0x150
[    0.310000]  [<ffffffff8154a2ea>] check_bugs+0x1a/0x20
[    0.310000]  [<ffffffff81540c4a>] start_kernel+0x2da/0x380
[    0.310000]  [<ffffffff81540132>] _sinittext+0x132/0x140
[    0.310000]
[    0.320000] ACPI: Core revision 20070126
[    0.560000] Using local APIC timer interrupts.
[    0.590000] Detected 62.496 MHz APIC timer.
[    0.590000] Brought up 1 CPUs

[ tglx: arch/x86 adaptation ]

Cc: Laurent Vivier <Laurent.Vivier@bull.net>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>