dma: xilinx: vdma: Change returning error codes

Change returning error codes to -ENXIO for xilinx_vdma_reset()
failure.

Signed-off-by: Hyun Kwon <hyunk@xilinx.com>
dma: xilinx: vdma: Don't disable interrupts at runtime

Enable interrupts when a channel is probed, and disable interrupts
only when a channel is removed. Re-enable interrupts
when a channel gets reset.

Signed-off-by: Hyun Kwon <hyunk@xilinx.com>
Acked-by: Srikanth Thokala <srikanth.thokala@xilinx.com>
dma: xilinx: vdma: Add xilinx_vdma_chan_reset() function

As interrupts are enabled in xilinx_vdma_chan_probe(),
interrupts should be re-enabled anytime when a vdma channle gets reset.
Add xilinx_vdma_chan_reset() which resets a vdma channel by calling
xilinx_vdma_reset(), and re-enables interrupts.

Signed-off-by: Hyun Kwon <hyunk@xilinx.com>
Acked-by: Srikanth Thokala <srikanth.thokala@xilinx.com>