mdss: display-port: fix register offsets for link training

Add proper register base and register address offsets
when configuring the voltage swings and preemphsis
settings. Fix interrupt register bit for VIDEO_READY.

Change-Id: I6e89f6fbb3660d13c186b38eb7ca1f71cbe8109d
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>