batman-adv: Reduce usage of char

char was used in different places to store information without really
using the characteristics of that data type or by ignoring the fact that
char has not a well defined signedness.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
diff --git a/net/batman-adv/bitarray.c b/net/batman-adv/bitarray.c
index 3659a25..c1f4bfc 100644
--- a/net/batman-adv/bitarray.c
+++ b/net/batman-adv/bitarray.c
@@ -127,8 +127,8 @@
  *  1 if the window was moved (either new or very old)
  *  0 if the window was not moved/shifted.
  */
-char bit_get_packet(void *priv, unsigned long *seq_bits,
-		    int32_t seq_num_diff, int8_t set_mark)
+int bit_get_packet(void *priv, unsigned long *seq_bits,
+		    int32_t seq_num_diff, int set_mark)
 {
 	struct bat_priv *bat_priv = priv;