powerpc/pcie: add PCIe version 3.x support

T4240 PCIe IP is version 3.0 and has some update comparing previous
QorIQ products.

1.  Move Freescale specific register define
to
arch/powerpc/include/asm/fsl_pci.h
and update the register offset define for T4240.

2. add the status/control register define
use status/control register to judge the link status

3. The original code uses 'Programming Interface' field to judge if PCIE is
EP or RC mode, however, T4240 does not support this functionality.
According to PCIE specification, 'Header Type' offset 0x0e is used to
indicate header type, so for PCIE controller, the patch changes code to
use 'Header Type' field to identify if the PCIE is RC or EP mode.

This patch fixes  the PCIe card link up issue on T4240QDS.

Signed-off-by: Roy Zang <tie-fei.zang@freescale.com>
Signed-off-by: Minghuan Lian <Minghuan.Lian@freescale.com>
Signed-off-by: York Sun <yorksun@freescale.com>