dmaengine: export symbol of of_dma_request_slave_channel()
dmaengine: export symbol of of_dma_request_slave_channel()

Current DMAEngine implementation of DT bindings can't support
DT subnode. This patch export symbols of of_dma_request_slave_channel()
for subnode DMA DT bingings.

ex)

rcar_sound: rcar_sound@ec500000 {
        ...
        rcar_sound,dvc {
                dvc0: dvc@0 {
                        dmas = <&audma0 0xbc>;
                        dma-names = "tx";
                };
                dvc1: dvc@1 {
                        dmas = <&audma0 0xbe>;
                        dma-names = "tx";
                };
        };
        ...
};

Signed-off-by: Kuninori Morimoto <a3b51ccb87d18302c1692defcfbf83319d1737eb@renesas.com>
Acked-by: Vinod Koul <5cf69c63beb17bf38d63aa0e923ee8256af0e205@intel.com>
Signed-off-by: Mark Brown <b51b9a92386687a9ac927cebfa0f978adeb8cea5@kernel.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs