display: Close 0 fds

0 can be a valid file descriptor, make sure 0 fds are closed

Change-Id: I2bf2280d70eda74fa0b0a886ea54ecefc6854b24
diff --git a/libhwcomposer/hwc_utils.cpp b/libhwcomposer/hwc_utils.cpp
index 093c0b3..a011f9b 100644
--- a/libhwcomposer/hwc_utils.cpp
+++ b/libhwcomposer/hwc_utils.cpp
@@ -390,11 +390,11 @@
         if(list->hwLayers[i].compositionType == HWC_OVERLAY ||
            list->hwLayers[i].compositionType == HWC_FRAMEBUFFER_TARGET) {
             //Close the acquireFenceFds
-            if(list->hwLayers[i].acquireFenceFd > 0) {
+            if(list->hwLayers[i].acquireFenceFd >= 0) {
                 close(list->hwLayers[i].acquireFenceFd);
                 list->hwLayers[i].acquireFenceFd = -1;
             }
-            if(fd > 0) {
+            if(fd >= 0) {
                 close(fd);
                 fd = -1;
             }