Revert "gralloc: Allow unmapping concurrent handles"

This reverts commit a3a9aaa5bb.

exynos4/hal/libgralloc_ump/gralloc_module.cpp

@@ -318,6 +318,8 @@ static int gralloc_unregister_buffer(gralloc_module_t const* module, buffer_hand
     ALOGE_IF(hnd->lockState & private_handle_t::LOCK_STATE_READ_MASK,
             "[unregister] handle %p still locked (state=%08x)", hnd, hnd->lockState);
 
+    /* never unmap buffers that were created in this process */
+    if (hnd->pid != getpid()) {
         pthread_mutex_lock(&s_map_lock);
         if (hnd->flags & private_handle_t::PRIV_FLAGS_USES_UMP) {
             ump_mapped_pointer_release((ump_handle)hnd->ump_mem_handle);
@@ -351,6 +353,7 @@ static int gralloc_unregister_buffer(gralloc_module_t const* module, buffer_hand
         }
 
         pthread_mutex_unlock(&s_map_lock);
+    }
 
     return 0;
 }