x86/apic: Modernize the pending interrupt code

The pending interrupt check code is old, update the following:

  - Use for_each_set_bit() instead of open coding it
  - Replace printk() with pr_err()
  - Get rid of printk line breaks
  - Make curly braces balanced

Suggested-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: bhe@redhat.com
Cc: ebiederm@xmission.com
Link: https://lkml.kernel.org/r/20180301055930.2396-3-douly.fnst@cn.fujitsu.com