libc: fix fstatfs() implementation.

The syscall expects the size of the buffer as the second argument.

Change-Id: I99ede2fec7fcd385ca03ff022c2cffa4297bea8d
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index bf65a6f..7626c45 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -120,7 +120,7 @@
 int         fchown:fchown32(int, uid_t, gid_t)  207
 void        sync(void)  36
 int         __fcntl64:fcntl64(int, int, void *)  221
-int         fstatfs:fstatfs64(int, size_t, struct statfs *)  267,269
+int         __fstatfs64:fstatfs64(int, size_t, struct statfs *)  267,269
 ssize_t     sendfile(int out_fd, int in_fd, off_t *offset, size_t count)  187
 int         fstatat:fstatat64(int dirfd, const char *path, struct stat *buf, int flags)   327,300
 int         mkdirat(int dirfd, const char *pathname, mode_t mode)  323,296