x86/irq: Drop unlikely before IS_ERR_OR_NULL

IS_ERR_OR_NULL already contain an unlikely compiler flag. Drop it.

Signed-off-by: Geliang Tang <geliangtang@163.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/03d18502ed7ed417f136c091f417d2d88c147ec6.1443667610.git.geliangtang@163.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>