drm/msm/dp: modify the max tx message size for hdcp2.2

This change modifies the max hdcp2.2 transmitter message
size to accommodate few messages greater than the
current maximum.

Change-Id: I2cf0f33252962cfbfc6be3f355276799c0f7f26a
Signed-off-by: Sankeerth Billakanti <sbillaka@codeaurora.org>