video: exynos_dp: fix max loop count in EQ sequence of link training

This patch fixes max loop count in EQ(Channel Equalization) sequence
of link training. According to DP(displayport) specification,
the max loop count in this sequence should be 5.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>