arch/arm/src/imxrt: This commit fixes more issues with the i.MX RT GPIO IRQ.

  imxrt_gpioirq.c
    - Add check for interrupt mask register before dispatching ISR. The GPIO_ISR bits are set independent of the GPIO_IMR bits.
  imxrt_irq.c
    - fixed a range check for extint in function imxrt_irqinfo().