dmaengine: dw-edma: Move eDMA data pointer to debugfs node descriptor

The last thing that stops the debugfs part of the eDMA driver from
supporting multi-eDMA platforms is keeping the eDMA private data pointer in
the static area of the debugfs module. Since the debugfs node descriptors
are now heap-allocated, we can freely move that pointer to being preserved
in the descriptors. After the debugfs initialization procedure, that
pointer will be used in the debugfs files getter to access the common CSRs
space and the context CSRs spinlock. So the main part of this change is
connected with the debugfs nodes descriptors initialization macros, which
aside with already defined prototypes now require to have the DW eDMA
private data pointer passed.

[bhelgaas: squash in https://lore.kernel.org/r/20230130185101.2883245-1-arnd@kernel.org]
Link: https://lore.kernel.org/r/20230113171409.30470-17-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>