dmaengine: imx-sdma: remove duplicated sdma_load_context

Since sdma_transfer_init() will do sdma_load_context before any
sdma transfer, no need once more in sdma_config_channel().

Fixes: ad0d92d7 ("dmaengine: imx-sdma: refine to load context only once")
Cc: <stable@vger.kernel.org>
Signed-off-by: Robin Gong <yibin.gong@nxp.com>
Acked-by: Vinod Koul <vkoul@kernel.org>
Tested-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>