powerpc/pci: fix PCI-e check link issue

For Freescale powerpc platform, the PCI-e bus number uses the reassign mode
by default. It means the second PCI-e controller's hose->first_busno is the
first controller's last bus number adding 1. For some hotpluged device(or
controlled by FPGA), the device is linked to PCI-e slot at linux runtime.
It needs rescan for the system to add it and driver it to work. It successes
to rescan the device linked to the first PCI-e controller's slot, but fails to
rescan the device linked to the second PCI-e controller's slot. The cause is
that the bus->number is reset to 0, which isn't equal to the hose->first_busno
for the second controller checking PCI-e link. So it doesn't really check the
PCI-e link status, the link status is always no_link. The device won't be
really rescaned. Reset the bus->number to hose->first_busno in the function
fsl_pcie_check_link(), it will do the real checking PCI-e link status for the
second controller, the device will be rescaned.

Signed-off-by: Yuanquan Chen <Yuanquan.Chen@freescale.com>
Tested-by: Rojhalat Ibrahim <imr@rtschenk.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>