dmaengine: lgm: Move DT parsing after initialization

ldma_cfg_init() will parse DT to retrieve certain configs.
However, that is called before ldma_dma_init_vXX(), which
will make some initialization to channel configs. It will
thus incorrectly overwrite certain configs that are declared
in DT.

To fix that, we move DT parsing after initialization.
Function name is renamed to better represent what it does.

Fixes: 32d31c79

 ("dmaengine: Add Intel LGM SoC DMA support.")
Signed-off-by: Peter Harliman Liem <pliem@maxlinear.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/afef6fc1ed20098b684e0d53737d69faf63c125f.1672887183.git.pliem@maxlinear.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>