drm/msm/dp: do a force dp_clean while dp disconnect

During connect notification timeout, a disconnect happens 
which also sends a disconnect notification to userspace
before post_enable which completes the semaphore early
and is leading to unclean deinit. USB performs a phy
reset during disconnect. On second connect, dp_host_init
finds core initialized thus creating a noc error while
accessing lclk.

Change-Id: I8c0fe6e9b0bf7c16cb996e534eee883957dc02d4
Signed-off-by: RAJAT GUPTA <rajatgu@codeaurora.org>