ath6kl: fix compiler warning in ath6kl_init_hw_params()

Both Luis and John reported that they see a compiler warning:

drivers/net/wireless/ath/ath6kl/init.c: In function 'ath6kl_init_hw_params':
drivers/net/wireless/ath/ath6kl/init.c:1377:26: warning: ‘hw’
may be used uninitialized in this function

Oddly enough I have never seen it. But AFAICT the code is correct and
hw is not used uninitalized so add uninitialized_var() to inform that to
the compiler.
Reported-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Reported-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/init.c

@@ -1470,7 +1470,7 @@ static int ath6kl_init_upload(struct ath6kl *ar)
 
 int ath6kl_init_hw_params(struct ath6kl *ar)
 {
-	const struct ath6kl_hw *hw;
+	const struct ath6kl_hw *uninitialized_var(hw);
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(hw_list); i++) {