dma: dma_nxp_edma: make sure channel is inactive when releasing

Make sure that channels are inactive before releasing them.
This way, there won't be any leftover interrupts needed to be
handled when disabling IRQs.

This patch introduces a new state: CHAN_STATE_RELEASING. This is mostly
useful for the per-channel PD support in which the ISR needs to check
that the channel PD is enabled before attempting to access its register
space.

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