ARM: dts: DRA7: Add pcie1 dt node for EP mode

Add pcie1 dt node in order for the controller to operate in
endpoint mode. However since none of the dra7 based boards have
slots configured to operate in endpoint mode, keep EP mode
disabled.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>