egl/android: enable/disable KHR_partial_update correctly

Commit f3728816 (egl/android: require ANDROID_native_fence_sync for buffer age) re-added some stale code removed in commit b4345da8 (egl/android: Delete set_damage_region from egl dri vtbl). Remove it now.

Commit b4345da8 assumes KHR_partial_update is only driver-dependent. That is mostly true except that the extension also introduces buffer age query, which depends on ANDROID_native_fence_sync on Android.

@lepton @woodychow @chadversary @krh