x86/io_apic: Make eoi_ioapic_pin() static

x86/io_apic: Make eoi_ioapic_pin() static

We have to define internally used function as static, otherwise the following
warning will be generated:

arch/x86/kernel/apic/io_apic.c:532:6: warning: no previous prototype for 'eoi_ioapic_pin' [-Wmissing-prototypes]

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/1444400685-98611-1-git-send-email-andriy.shevchenko@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>