msm: mdss: support reduced dspp and WB interfaces

MDSS driver has condition check for 1:1 mapping for dspp to
interface and WB to ctrl. This check is not valid for all MDP
version hardware.  It can support less dspp compared to number
of interfaces. It can also support less number of WB paths
compared to controllers. This change enables MDSS driver
to handle such hardware conditions.

Change-Id: Ic08e274c73cc41e80245a0d3d4ae7b854bd5a2d3
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>