ARM: dts: exynos: Use stdout-path property instead of console in bootargs

Replacing bootargs with stdout-path property in chosen node allows using
early console by adding just 'earlycon' parameter to the kernel command
line.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>