ARM: dts: change compatible value for exynos5440 i2c

This patch removes disabled status from I2C node for exynos5440-ssdk5440,
and fixes the incorrect compatible property value of i2c for exynos5440.

Signed-off-by: Giridhar Maruthy <giridhar.m@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>