printk: make _char_out globally accessible

This is to support a printf test case where we need to know
the existing value so we can chain it.

Change-Id: I671429aa7dab1391840f49f54cc6c23baccf265c
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/misc/printk.c b/misc/printk.c
index a5bd8e4..5bcc761 100644
--- a/misc/printk.c
+++ b/misc/printk.c
@@ -44,7 +44,7 @@
 	return 0;
 }
 
-static int (*_char_out)(int) = _nop_char_out;
+int (*_char_out)(int) = _nop_char_out;
 
 
 /**