dmaengine: dw-edma: Add dw_edma prefix to debugfs nodes descriptor

Other local names include a "dw_edma" prefix.

Add a "dw_edma" prefix to the debugfs_entries structure, too, so it won't
be confused with global debugfs things.

Link: https://lore.kernel.org/r/20230113171409.30470-13-Sergey.Semin@baikalelectronics.ru


Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>