PCI: dwc: dra7xx: Assign pp->ops in dra7xx_add_pcie_port() rather than in probe

Assign pp->ops in *_add_pcie_port() to match how it is done in other
drivers like exynos, imx7, keystone, armada8k, artpec6, designware-plat,
hisi, kirin and spear13xx.

This is probably a remainder since when dev and ops were assigned as
members to pp. Since we now assign them as members to struct dw_pcie,
the pp->ops assignment should definitely be in dra7xx_add_pcie_port().

This is done so that the compiler (in a later commit) can remove more
code when enabling only one of the two supported modes (host/ep) in
the dra7xx driver.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>