hwc: Rotate RGB layer using MDP Rotator

1. Use MDP rotator to rotate RGB layers which are rendered by software
2. Restrict total number of rotator sessions to 4 for all displays
3. Disable RGB layer rotation for all MDP versions < MDP5

Change-Id: Ie93111082dff9a16b614e9768df5d8ce83ff9e25

libgralloc/gpu.cpp

@@ -152,6 +152,10 @@ int gpu_context_t::gralloc_alloc_buffer(unsigned int size, int usage,
             flags |= private_handle_t::PRIV_FLAGS_TILE_RENDERED;
         }
 
+        if(usage & (GRALLOC_USAGE_SW_READ_MASK | GRALLOC_USAGE_SW_WRITE_MASK)) {
+            flags |= private_handle_t::PRIV_FLAGS_CPU_RENDERED;
+        }
+
         flags |= data.allocType;
         uint64_t eBaseAddr = (uint64_t)(eData.base) + eData.offset;
         private_handle_t *hnd = new private_handle_t(data.fd, size, flags,