p54: eliminate warning for uninitialized variable 'tim_len'

drivers/net/wireless/p54/p54common.c: In function ‘p54_tx’:
drivers/net/wireless/p54/p54common.c:1058: warning: ‘tim_len’ may be used uninitialized in this function

Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/p54/p54common.c b/drivers/net/wireless/p54/p54common.c
index 8423c43..a2e2150 100644
--- a/drivers/net/wireless/p54/p54common.c
+++ b/drivers/net/wireless/p54/p54common.c
@@ -1054,7 +1054,7 @@
 	struct p54_common *priv = dev->priv;
 	struct p54_hdr *hdr;
 	struct p54_tx_data *txhdr;
-	size_t padding, len, tim_len;
+	size_t padding, len, tim_len = 0;
 	int i, j, ridx;
 	u16 hdr_flags = 0, aid = 0;
 	u8 rate, queue;