MLK-10009-4 PCI: designware: Refine setup_rc and add msi data restore

- move "program correct class for RC" from dw_pcie_host_init()
to dw_pcie_setup_rc(). since this is RC setup, it's
better to contained in dw_pcie_setup_rc function.
Then, RC can be re-setup really by dw_pcie_setup_rc().
- add one store/re-store msi cfg functions. Because that
pcie controller maybe powered off during system suspend,
and the msi data configuration would be lost.
these functions can be used to store/restore the msi data
and msi_enable during the suspend/resume callback.

Signed-off-by: Richard Zhu <richard.zhu@freescale.com>