pci: tegra: Make clkport independent of root port

pci: tegra: Make clkport independent of root port

PCI driver assumes that PCI0 is bound to clock port 0 and PCI1 is bound
to clock port 1. This patch adds a DT property to make use of the below
combinations as well
PCI0 <--> Clock Port 1
PCI1 <--> Clock Port 0

bug 1657220

Change-Id: I01ff0285d1b1403f1ea15202119318fb489fbe8b
Signed-off-by: Vipin Kumar <vipink@nvidia.com>
Reviewed-on: http://git-master/r/801253
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>