dmaengine: dw-edma: Stop checking debugfs_create_*() return value

dmaengine: dw-edma: Stop checking debugfs_create_*() return value

The debugfs_create_*() functions never return NULL, so checking their
return value for NULL is pointless. Secondly, the debugfs subsystem is
designed to be as simple as possible, so if one of the debugfs_create_*()
method in a hierarchy fails, the following methods should silently return
the passed erroneous parental dentry. Finally, the code should work no
matter whether anything debugfs-related fails.

To make code simpler and debugfs-independent, stop checking the
debugfs_create_*() return values.

If the debugfs file system is unavailable, skip the debugfs node
initialization altogether to preserve some memory space.

Link: https://lore.kernel.org/r/20230113171409.30470-12-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>