hdcp_qseecom: Add support for DP MST feature

Adding open and close stream APIs to support Display
Port MST feature. Also added streamNumber in open
stream API.

Change-Id: Icf6e7adebae7d4d388f7cfaedd4bb17908817d10
Signed-off-by: Shivaprasad Hongal <shongal@codeaurora.org>