iwlwifi: dump stack when fail to gain access to the device

Print dump stack when the device is not responding. This should give
some more clue about the reason of failure. Also change the message we
print, since "MAC in deep sleep" is kinda confusing.

On the way add unlikely(), as fail to gain NIC access is hmm ...
unlikely.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-io.c

@@ -121,10 +121,10 @@ int iwl_grab_nic_access_silent(struct iwl_trans *trans)
 int iwl_grab_nic_access(struct iwl_trans *trans)
 {
 	int ret = iwl_grab_nic_access_silent(trans);
-	if (ret) {
+	if (unlikely(ret)) {
 		u32 val = iwl_read32(trans, CSR_GP_CNTRL);
-		IWL_ERR(trans,
-			"MAC is in deep sleep!. CSR_GP_CNTRL = 0x%08X\n", val);
+		WARN_ONCE(1, "Timeout waiting for hardware access "
+			     "(CSR_GP_CNTRL 0x%08x)\n", val);
 	}
 
 	return ret;