PCI: kirin: Make structure kirin_dw_pcie_ops constant

Static variable kirin_dw_pcie_ops, of type dw_pcie_ops, is used only
once, when it is assigned to the constant field ops of variable pci
(having type dw_pcie) so kirin_dw_pcie_ops is never modified.

Make it constant to protect it from unintended modification.

Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrew Murray <andrew.murray@arm.com>