dts: atmel/nxp: supress duplicate unit-address warning

A number of SoCs have overlapping devices at the same unit address.
Surpress the warning for those cases:

* Atmel - pinmux@41004400 & gpio@41004400
* Atmel - pinmux@41004480 & gpio@41004480
* Atmel - pinmux@41008000 & gpio@41008000
* NXP - flash@0 & gpio@0
* NXP - syscon@0 & gpio@0

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>