msm: mdss: cleanup dsi clock handling

Currently the DSI driver uses a two level reference counting for
the clocks used by the driver so as to ensure that the clocks are
correctly configured for dual-dsi use cases. However, this is not
necessary as the same can be achieved by using a single reference
count. Clean up the code to remove the sub-level ref counts and
add necessary error handling.

Change-Id: I6f1c1bfe83322dc0e1da3d757b6ca88cd629663e
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>
msm: mdss: Add support to selectively control bus and link clocks

DSI driver needs two different types of clocks for normal
operation - bus clocks and link clocks. The clock control function
enables/disables both these set of clocks together. However,
under certain circumstances, it is required to control just the
link clocks or the bus clocks. To support this, add separate
ref counts for link and bus clocks and modify the clock control
function to selectively control these clocks.

Change-Id: I25312131fc737b56dc15f4edf5e55a5824dad855
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>
msm: mdss: Turn on DSI link clocks after exiting ULPS

DSI branch clocks should only be enabled after removing the DSI clamps
when exiting the Ultra Low Power State (ULPS). If this is not enforced,
then the RCG for these clocks may not get turned on correctly which
may eventually lead to some display corruption. Fix this by
appropriately modifying ULPS exit sequence.

Change-Id: I5109dd140f8921256f95eb479dd33a73615d489f
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>