alpha: Replace setup_irq() by request_irq()

request_irq() is preferred over setup_irq(). Invocations of setup_irq()
occur after memory allocators are ready.

setup_irq() was required in older kernels as the memory allocator was not
available during early boot.

Hence replace setup_irq() by request_irq().

Signed-off-by: afzal mohammed <afzal.mohd.ma@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Matt Turner <mattst88@gmail.com>
Link: https://lkml.kernel.org/r/51f8ae7da9f47a23596388141933efa2bdef317b.1585320721.git.afzal.mohd.ma@gmail.com