PCI: dw-rockchip: Reorganize register and bitfield definitions

Register definitions were scattered with ambiguous names (e.g.,
PCIE_RDLH_LINK_UP_CHGED in PCIE_CLIENT_INTR_STATUS_MISC) and lacked
hierarchical grouping.

Group registers and their associated bitfields logically. This improves
maintainability and aligns the code with hardware documentation.

Signed-off-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://patch.msgid.link/20250427125316.99627-3-18255117159@163.com