drivers/gpu/drm/i915/i915_irq.c:i915_error_object_create(): use correct kmap-atomic slot

i915_error_object_create() is called from the timer interrupt and hence
can corrupt the KM_USER0 slot.  Use KM_IRQ0 instead.

Reported-by: Jaswinder Singh Rajput <jaswinderlinux@gmail.com>
Tested-by: Jaswinder Singh Rajput <jaswinderlinux@gmail.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>