cw1200: fix bogus maybe-uninitialized warning

On x86, the cw1200 driver produces a rather silly warning about the
possible use of the 'ret' variable without an initialization
presumably after being confused by the architecture specific definition
of WARN_ON:

drivers/net/wireless/st/cw1200/wsm.c: In function ‘wsm_handle_rx’:
drivers/net/wireless/st/cw1200/wsm.c:1457:9: error: ‘ret’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

We have already checked that 'count' is larger than 0 here, so
we know that 'ret' is initialized. Changing the 'for' loop
into do/while also makes this clear to the compiler.
Suggested-by: David Laight <David.Laight@ACULAB.COM>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/st/cw1200/wsm.c

@@ -379,7 +379,6 @@ static int wsm_multi_tx_confirm(struct cw1200_common *priv,
 {
 	int ret;
 	int count;
-	int i;
 
 	count = WSM_GET32(buf);
 	if (WARN_ON(count <= 0))
@@ -395,11 +394,10 @@ static int wsm_multi_tx_confirm(struct cw1200_common *priv,
 	}
 
 	cw1200_debug_txed_multi(priv, count);
-	for (i = 0; i < count; ++i) {
+	do {
 		ret = wsm_tx_confirm(priv, buf, link_id);
-		if (ret)
-			return ret;
-	}
+	} while (!ret && --count);
+
 	return ret;
 
 underflow: