msmcobalt: hwc fix compilation error on master

Change-Id: I6db96de289b0a4c206850e901702a2f24ca1b62a
diff --git a/msmcobalt/sdm/libs/hwc/hwc_session.cpp b/msmcobalt/sdm/libs/hwc/hwc_session.cpp
index b00968c..a980e12 100644
--- a/msmcobalt/sdm/libs/hwc/hwc_session.cpp
+++ b/msmcobalt/sdm/libs/hwc/hwc_session.cpp
@@ -1343,7 +1343,7 @@
 int HWCSession::GetEventValue(const char *uevent_data, int length, const char *event_info) {
   const char *iterator_str = uevent_data;
   while (((iterator_str - uevent_data) <= length) && (*iterator_str)) {
-    char *pstr = strstr(iterator_str, event_info);
+    const char *pstr = strstr(iterator_str, event_info);
     if (pstr != NULL) {
       return (atoi(iterator_str + strlen(event_info)));
     }