drm/msm/dp: time out after reaching link training max retries

Time out after reaching the link training max retries to ensure
that the link training controlling loop exits. If we do not time
out in the face of continuous link training failure then the link
training loop will will be infinite. Example: an unrecoverable
link failure will trigger a link maintenance infinite loop if we
do not time out.

CRs-Fixed: 2094794
Change-Id: I97795132ecfad93ffab171ecd4e75cf9831c1da6
Signed-off-by: Tatenda Chipeperekwa <tatendac@codeaurora.org>