display: Return MDP pipe availability per display type

Pipes allocated for one display type cannot be used by other
display types without calling UNSET on them. So clients should
check for pipe availablity only for a specific display type.

Change-Id: Id2244e4976b4cc1f040ada7e56686742d5a65141

CRs-Fixed: 433870
diff --git a/libhwcomposer/hwc_mdpcomp.cpp b/libhwcomposer/hwc_mdpcomp.cpp
index c65c056..2c0a77a 100644
--- a/libhwcomposer/hwc_mdpcomp.cpp
+++ b/libhwcomposer/hwc_mdpcomp.cpp
@@ -369,7 +369,7 @@
     int numAppLayers = ctx->listStats[dpy].numAppLayers;
 
     overlay::Overlay& ov = *ctx->mOverlay;
-    int availablePipes = ov.availablePipes();
+    int availablePipes = ov.availablePipes(dpy);
 
     if(numAppLayers < 1 || numAppLayers > (uint32_t)availablePipes) {
         ALOGD_IF(isDebug(), "%s: Unsupported number of layers",__FUNCTION__);