of/irq: Get rid of NO_IRQ usage

PPC32/64 defines NO_IRQ to zero, so no problems expected.
ARM defines NO_IRQ to -1, but OF code relies on IRQ domains support,
which returns correct ('0') value in 'no irq' case. So everything
should be fine.

Other arches might break if some of their OF drivers rely on NO_IRQ
being not 0. If so, the drivers must be fixed, finally.

[ Rob Herring points out that microblaze should be fixed, and has posted
  a patch for testing for that.   - Linus ]

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>