imxtools: use rand() instead of /dev/random.

On Windows /dev/random does not exist, so trying to open it will fail. Replace
it with rand() which is available on all supported platforms and sufficient.

Fixes mkimxboot not working, as well as Rockbox Utility "crashing" (which is in
fact its error handler calling exit(), thus terminating Rockbox Utility) on
Windows.

Change-Id: Ia164f937f329877e8f80f473f27be8c5df2a0a68

Author: bluebrother

utils/imxtools/misc.c

@@ -39,12 +39,10 @@ void *memdup(const void *p, size_t len)
 
 void generate_random_data(void *buf, size_t sz)
 {
-    FILE *rand_fd = fopen("/dev/urandom", "rb");
-    if(rand_fd == NULL)
-        bugp("failed to open /dev/urandom");
-    if(fread(buf, 1, sz, rand_fd) != sz)
-        bugp("failed to read /dev/urandom");
-    fclose(rand_fd);
+    int i = 0;
+    unsigned char* p = (unsigned char*)buf;
+    while(i++ < sz)
+        *p++ = rand();
 }
 
 void *xmalloc(size_t s)