Fix names of headtracking feature files.

Test: build
Bug: 36294374
Change-Id: I04fc2478a339a6bffd6b04c633478d6b8740ac3e
diff --git a/data/etc/android.hardware.vr.headtracking-0.mxl b/data/etc/android.hardware.vr.headtracking-0.xml
similarity index 100%
rename from data/etc/android.hardware.vr.headtracking-0.mxl
rename to data/etc/android.hardware.vr.headtracking-0.xml
diff --git a/data/etc/android.hardware.vr.headtracking-1.mxl b/data/etc/android.hardware.vr.headtracking-1.xml
similarity index 100%
rename from data/etc/android.hardware.vr.headtracking-1.mxl
rename to data/etc/android.hardware.vr.headtracking-1.xml