ARM: keystone: dts: rename pcie nodes to help override status

Now that PCIe DT binding is disabled in SoC specific DTS,
we need a way to override it in a board specific DTS. So
rename the PCIe nodes accordingly.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>