linux-user: initialize mmap_mutex properly

We initialize mmap_mutex in any child threads/processes, but we need to
correctly statically initialize it for the original process.
Signed-off-by: NNathan Froyd <froydnj@codesourcery.com>
Signed-off-by: NRiku Voipio <riku.voipio@iki.fi>

linux-user/mmap.c

@@ -36,7 +36,7 @@
 //#define DEBUG_MMAP
 
 #if defined(USE_NPTL)
-pthread_mutex_t mmap_mutex;
+pthread_mutex_t mmap_mutex = PTHREAD_MUTEX_INITIALIZER;
 static int __thread mmap_lock_count;
 
 void mmap_lock(void)