drivers: dma: dma_nxp_edma: disable IRQs when not needed

IRQs are currently only enabled during channel setup
and never disabled. As such, even though they're not
needed (i.e: after a channel has been suspended or stopped)
they remain enabled. Fix this by enabling IRQs during the
channel start() operation and disabling them during the
channel stop() operation.

This change is required by irq chips (i.e: irqsteer) which
perform PM operations during irq_enable()/irq_disable(). If
interrupts are left enabled all the time that means the irq
chip's PM resources might also remain enabled when not needed.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>