dmaengine: Update documentation for inline wrappers

During the last few years, several inline wrappers for DMA operations have
been introduced:
  - commit 16052827 ("dmaengine/dma_slave:
    introduce inline wrappers"),
  - commit a14acb4a ("DMAEngine: add
    dmaengine_prep_interleaved_dma wrapper for interleaved api"),
  - commit 6e3ecaf0 ("dmaengine: add
    wrapper functions for device control functions").

Update the documentation to use the wrappers.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>