Move the PLDA generic data structures to a header file so they can be
re-used by all PLDA-based drivers.

[kwilczynski: commit log]
Link: https://lore.kernel.org/linux-pci/20240328091835.14797-7-minda.chen@starfivetech.comSigned-off-by: Minda Chen <minda.chen@starfivetech.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>