sta_get_parameter: Avoid NULL pointer access on error paths for PMK

The goto fail implementation due to pos=NULL while searching for PMK
in the PMKSA_GET response could result in accessing pos to search for
'\n'. Avoid this by not doing a "goto fail" but rather break the while
loop for any improper format in the line corresponding to PMK.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
diff --git a/sta.c b/sta.c
index 5e61be1..71a2346 100644
--- a/sta.c
+++ b/sta.c
@@ -6690,20 +6690,18 @@
 		if (strncmp(pos, bssid, 17) == 0) {
 			pos = strchr(pos, ' ');
 			if (!pos)
-				goto fail;
+				break;
 			pos++;
 			pos = strchr(pos, ' ');
 			if (!pos)
-				goto fail;
+				break;
 			pos++;
 			tmp = strchr(pos, ' ');
 			if (!tmp)
-				goto fail;
+				break;
 			*tmp = '\0';
 			break;
 		}
-
-	fail:
 		pos = strchr(pos, '\n');
 		if (pos)
 			pos++;