defer firmware load until after filesystems are mounted

In some situations a driver could try to request firmware before
/system is mounted.  Previously we'd fail the request.  Now we
will retry the read-from-filesystem every 100ms until we find the
firmware or we've finished the "fs" and "post-fs" stages of init.

Change-Id: Ie32402f7d41c818bf20f3297286ed5f99705b72c
diff --git a/init/ueventd.c b/init/ueventd.c
index 0e97be7..1328d19 100644
--- a/init/ueventd.c
+++ b/init/ueventd.c
@@ -20,6 +20,8 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <ctype.h>
+#include <signal.h>
+
 #include <private/android_filesystem_config.h>
 
 #include "ueventd.h"
@@ -37,6 +39,13 @@
     int nr;
     char tmp[32];
 
+        /* Prevent fire-and-forget children from becoming zombies.
+         * If we should need to wait() for some children in the future
+         * (as opposed to none right now), double-forking here instead
+         * of ignoring SIGCHLD may be the better solution.
+         */
+    signal(SIGCHLD, SIG_IGN);
+
     open_devnull_stdio();
     log_init();