tty: Remove private constant from global namespace

TTY_BUFFER_PAGE is only used within drivers/tty/tty_buffer.c;
relocate to that file scope.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
index f22e116..c043136f 100644
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -28,6 +28,16 @@
  */
 #define TTYB_MEM_LIMIT	65536
 
+/*
+ * We default to dicing tty buffer allocations to this many characters
+ * in order to avoid multiple page allocations. We know the size of
+ * tty_buffer itself but it must also be taken into account that the
+ * the buffer is 256 byte aligned. See tty_buffer_find for the allocation
+ * logic this must match
+ */
+
+#define TTY_BUFFER_PAGE	(((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF)
+
 
 /**
  *	tty_buffer_lock_exclusive	-	gain exclusive access to buffer