Update for cleanups in hwc interface

Also store the hwc_procs_t* into a dedicated field instead of one of
the hwc_composer_device_1_t::reserved_procs slots, which are supposed
to be NULL so the structure can be extended without breaking backwards
binary compatibility.

Change-Id: I11e6bc713958d854aba418242caa749cbcb21f1d
diff --git a/libhwcomposer/hwc_external.cpp b/libhwcomposer/hwc_external.cpp
index c4a6a6a..d35a622 100644
--- a/libhwcomposer/hwc_external.cpp
+++ b/libhwcomposer/hwc_external.cpp
@@ -385,16 +385,9 @@
         const char* prop = (connected) ? "1" : "0";
         // set system property
         property_set("hw.hdmiON", prop);
-        //Invalidate
-        hwc_procs* proc = (hwc_procs*)ctx->device.reserved_proc[0];
-        if(!proc) {
-            ALOGE("%s: HWC proc not registered",
-                     __FUNCTION__);
-        } else {
-            /* Trigger redraw */
-            ALOGD_IF(DEBUG, "%s: Invalidate !!", __FUNCTION__);
-            proc->invalidate(proc);
-        }
+        /* Trigger redraw */
+        ALOGD_IF(DEBUG, "%s: Invalidate !!", __FUNCTION__);
+        ctx->proc->invalidate(ctx->proc);
     }
     return;
 }