Make various things static

Building an allnoconfig kernel, sparse asked whether these could be
static, so I checked, and they are only used in the file where they are
declared.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 112a6ba..146c976 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -32,7 +32,7 @@
 
 /* These are global because they are accessed in tty_io.c */
 #ifdef CONFIG_UNIX98_PTYS
-struct tty_driver *ptm_driver;
+static struct tty_driver *ptm_driver;
 static struct tty_driver *pts_driver;
 #endif