keystore: fix inverted hardware keystore check

Check should be that the 'is_software' flag is off.

Change-Id: Ic03ef957f6aa62b959b24fe8e4ff202f431aab89
diff --git a/keystore/keystore.cpp b/keystore/keystore.cpp
index 34cab24..760ec4d 100644
--- a/keystore/keystore.cpp
+++ b/keystore/keystore.cpp
@@ -753,7 +753,7 @@
     }
 
     bool isHardwareBacked() const {
-        return (mDevice->flags & KEYMASTER_SOFTWARE_ONLY) != 0;
+        return (mDevice->flags & KEYMASTER_SOFTWARE_ONLY) == 0;
     }
 
 private: