powerpc: Make open count variables signed in hvcs/hvsi/hvc_console

Otherwise the tests for count < 0 will never be true.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/drivers/char/hvcs.c b/drivers/char/hvcs.c
index 473d9b1..6e6eb44 100644
--- a/drivers/char/hvcs.c
+++ b/drivers/char/hvcs.c
@@ -269,7 +269,7 @@
 	unsigned int index;
 
 	struct tty_struct *tty;
-	unsigned int open_count;
+	int open_count;
 
 	/*
 	 * Used to tell the driver kernel_thread what operations need to take