dmaengine: intel-mid-dma: remove the driver

Since the last and the only user of this driver is converted to use dw_dmac we
can remove driver from the tree.

Moreover, besides the driver is unmaintained a long time, it serves for the
DesignWare DMA IP, for which we have already driver in the tree.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>