dmaengine: mediatek: uart-apdma: Get addressing bits from match data

dmaengine: mediatek: uart-apdma: Get addressing bits from match data

The only SoC that declares mediatek,dma-33bits in its devicetree
currently is MT6795, which obviously also declares a SoC-specific
compatible string: in preparation for adding new SoCs with 34 bits
addressing, replace the parsing of said vendor property with logic
to get the number of addressing bits from platform data associated
to compatible strings.

While at it, also make the bit_mask variable unsigned and move the
`int rc` declaration as last to beautify the code.

Thanks to the correct declaration of the APDMA node is in all of
the MediaTek device trees that are currently upstream, this commit
brings no functional differences.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20251113122229.23998-5-angelogioacchino.delregno@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>