dmaengine: omap-dma: Fix dynamic lch_map allocation

The original patch did not done what it was supposed to be doing and even
worst it broke legacy boot (OMAP1).

The lch_map size should be the number of available logical channels in sDMA
and the od->dma_requests should store the number of available DMA request
lines usable in sDMA.

In legacy mode we do not have a way to get the DMA request count, in that
case we use OMAP_SDMA_REQUESTS (127), despite the fact that OMAP1510 have
only 31 DMA request line.

Fixes: 2d1a9a94

 ("dmaengine: omap-dma: Dynamically allocate memory for lch_map")
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: stable@vger.kernel.org   # v4.9
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>