linux-phytec-ti

pci-dra7xx: add dts option for enabling clocks

Added support to control the output enable for
the PCIe clock generator IC on the PHYTEC
phyCORE-AM57xx RDK. The output enable pin is
connected to a GPIO.

clk_oe is obtained from the dts via the second gpios entry,
and it is optional so this will not break functionality
for any other boards.

Signed-off-by: Russell Robinson <rrobinson@phytec.com>