dmaengine: axi-dmac: add support for reading bus attributes from registers

Starting with core version 4.3.a the DMA bus attributes can (and should) be
read from the INTERFACE_DESCRIPTION (0x10) register.

For older core versions, this will still need to be provided from the
device-tree.

The bus-type values are identical to the ones stored in the device-trees,
so we just need to read them. Bus-width values are stored in log2 values,
so we just need to use them as shift values to make them equivalent to the
current format.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200825151950.57605-7-alexandru.ardelean@analog.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>