fixup! ARM: brcmstb: drop redundant IRQ disable
ARM: brcmstb: don't panic() on failed cpu_die()

panic() will access shared kernel structures, but the dying CPU is
already in non-coherent mode. So don't do this.

Just loop forever, since we'll likely notice there's a problem as soon
as we try to power this CPU down anyway.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>