dt-bindings: PCI: ti,j721e-pci-*: Add "ti,syscon-pcie-refclk-out" property

commit 6df1ab1935868ed950a656473023257eeaa31c35 from
git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git



Added "ti,syscon-pcie-refclk-out" property to specify the ACSPCIE clock
buffer register offset in SYSCON, which would be used to enable serdes
reference clock output.

Signed-off-by: Achal Verma <a-verma1@ti.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>