InputDevice warning fixes and make warnigs into Error

use const char * for string literals in InputDevice
Remove unused variable in Keyboard

Bug: 35993509
Test: mm in frameworks/native/libs/input builds without the warning
Change-Id: I11242835eae855386c47e56d6c36e5a2f912a28f
diff --git a/libs/input/InputDevice.cpp b/libs/input/InputDevice.cpp
index 9d761fd..4287abe 100644
--- a/libs/input/InputDevice.cpp
+++ b/libs/input/InputDevice.cpp
@@ -90,7 +90,7 @@
     String8 path;
 
     // Treblized input device config files will be located /odm/usr or /vendor/usr.
-    char *rootsForPartition[] {"/odm", "/vendor", getenv("ANDROID_ROOT")};
+    const char *rootsForPartition[] {"/odm", "/vendor", getenv("ANDROID_ROOT")};
     for (size_t i = 0; i < size(rootsForPartition); i++) {
         path.setTo(rootsForPartition[i]);
         path.append("/usr/");