ARM: EXYNOS: Add AUXDATA for DP controller

Use AUXDATA to set the device names for DP controller instance
discovered from device tree.

Signed-off-by: Ajay Kumar <ajaykumar.rs@samsung.com>
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>