dmaengine: sun6i: Set the maximum segment size

dmaengine: sun6i: Set the maximum segment size

The sun6i DMA engine supports segment sizes up to 2^25-1 bytes. This is
explicitly stated in newer SoC documentation (H6, D1), and it is implied
in older documentation by the 25-bit width of the "bytes left in the
current segment" register field.

Exposing the real segment size limit (instead of the 64k default)
reduces the number of SG list segments needed for a transaction.

Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Link: https://lore.kernel.org/r/20230101193605.50285-1-samuel@sholland.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>