Input: lpc32xx-keys - fix invalid error handling of a requested irq

Semantics of NR_IRQS is different on machines with SPARSE_IRQ option
disabled or enabled, in the latter case IRQs are allocated starting
at least from the value specified by NR_IRQS and going upwards, so
the check of (irq >= NR_IRQ) to decide about an error code returned by
platform_get_irq() is completely invalid, don't attempt to overrule
irq subsystem in the driver.

The change fixes lpc32xx_keys driver initialization on boot:

  lpc32xx_keys 40050000.key: failed to get platform irq
  lpc32xx_keys: probe of 40050000.key failed with error -22

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Acked-by: Sylvain Lemieux <slemieux.tyco@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>