MAINTAINERS: Remove Jason Cooper's irqchip git tree

Jason's irqchip tree does not seem to have been updated for many months
now, remove it from the list of trees to avoid any possible confusion.

Jason says:

  "Unfortunately, when I have time for irqchip, I don't always have the
   time to properly follow up with pull-requests. So, for the time being,
   I'll stick to reviewing as I can."

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Jason Cooper <jason@lakedaemon.net>
Cc: marc.zyngier@arm.com
Link: http://lkml.kernel.org/r/20170727224733.8288-1-f.fainelli@gmail.com