ARM: dts: Fix typo earlyprintk in exynos5440-sd5v1 and ssdk5440 boards

This patch removes '_' from "early_prink" on Exynos5440 dts
files in according to kernel-parameters document.

Signed-off-by: Youngmin Nam <youngmin.nam@samsung.com>
Reviewed-by: Sachin Kamat <sachin.kamat@linaro.org>
Tested-by: Jungseok Lee <jays.lee@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>