ARM: dts: am437x: make edt-ft5x06 a wakeup source

[ Upstream commit 49a6ec5b807ea4ad7ebe1f58080ebb8497cb2d2c ]

The touchscreen driver no longer configures the device as wakeup source by
default. A "wakeup-source" property is needed.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>