asan: Fix malloc/free mismatch for fb device

bug: 116981035

fb device was previously allocated with malloc
and freed with delete, not free.

Uncovered from running goldfish-opengl host side test
wih ASAN enabled.

Change-Id: I46b97d212e0baf47cd3d181f1b75ce27cb955fad

system/gralloc/gralloc.cpp

@@ -956,7 +956,7 @@ static int fb_close(struct hw_device_t *dev)
 {
     fb_device_t *fbdev = (fb_device_t *)dev;
 
-    delete fbdev;
+    free(fbdev);
 
     return 0;
 }