ath6kl: fix compilation warning in ath6kl_htc_pipe_conn_service

Fix the warning

drivers/net/wireless/ath/ath6kl/htc_pipe.c: In function
'ath6kl_htc_pipe_conn_service':
drivers/net/wireless/ath/ath6kl/htc_pipe.c:1293:26: warning: integer overflow
in expression [-Woverflow]

by giving a hint to compiler about unsigned nature of
HTC_CONN_FLGS_SET_RECV_ALLOC_MASK
Signed-off-by: Vladimir Murzin <murzin.v@gmail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>

drivers/net/wireless/ath/ath6kl/htc.h

@@ -60,7 +60,7 @@
 /* disable credit flow control on a specific service */
 #define HTC_CONN_FLGS_DISABLE_CRED_FLOW_CTRL          (1 << 3)
 #define HTC_CONN_FLGS_SET_RECV_ALLOC_SHIFT    8
-#define HTC_CONN_FLGS_SET_RECV_ALLOC_MASK     0xFF00
+#define HTC_CONN_FLGS_SET_RECV_ALLOC_MASK     0xFF00U
 
 /* connect response status codes */
 #define HTC_SERVICE_SUCCESS      0