arm64: dts: ti: k3-am625-sk-lpmdemo/skeleton: Fix low power mode

Commit 678e7dad ("arm64: dts: ti: k3-am62: add watchdog nodes")
introduced watchdog nodes but they break low power mode.
They are not required for boot so keep them disabled in
k3-am625-skeleton.dts

Fixes: 678e7dad

 ("arm64: dts: ti: k3-am62: add watchdog nodes")
Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Georgi Vlaev <g-vlaev@ti.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>