Fix CON_BUF_SIZE usage

Index: tiny/drivers/char/vt.c
===================================================================
@@ -1864,7 +1864,7 @@
  * since console_init (and thus con_init) are called before any
  * kernel memory allocation is available.
  */
-char con_buf[PAGE_SIZE];
+char con_buf[CON_BUF_SIZE];
 DECLARE_MUTEX(con_buf_sem);
 
 /* acquires console_sem */

Index: tiny/include/linux/vt_kern.h
===================================================================
@@ -89,8 +89,8 @@
  * vc_screen.c shares this temporary buffer with the console write code so that
  * we can easily avoid touching user space while holding the console spinlock.
  */
-extern char con_buf[PAGE_SIZE];
 #define CON_BUF_SIZE	PAGE_SIZE
+extern char con_buf[CON_BUF_SIZE];
 extern struct semaphore con_buf_sem;
 
 #endif /* _VT_KERN_H */