lib: posix: fs: Don't depend on pthreads

File system access isn't related to pthreads.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
diff --git a/lib/posix/fs.c b/lib/posix/fs.c
index 4d4bc1e..803a34d 100644
--- a/lib/posix/fs.c
+++ b/lib/posix/fs.c
@@ -7,7 +7,6 @@
 #include <errno.h>
 #include <kernel.h>
 #include <limits.h>
-#include <posix/pthread.h>
 #include <posix/unistd.h>
 #include <posix/dirent.h>
 #include <string.h>