dt-bindings: dma-engine: sifive,fu540: Add dma-channels property and modify compatible

Add dma-channels property, then we can determine how many channels there
by device tree, rather than statically defining it in PDMA driver.
In addition, we also modify the compatible for PDMA versioning scheme.

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Suggested-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Link: https://lore.kernel.org/r/7cc9a7b5f7e6c28fc9eb172c441b5aed2159b8a0.1648461096.git.zong.li@sifive.com


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