Add android:configChanges for SettingsHomepageActivity

When resuming Settings app of large screen devices,
SettingsHomepageActivity will be re-created for
Activity resized. It produces unnecessary Activity
destroy and re-create.

This change prevents SettingsHomepageActivity from
configuration changes for screenSize|screenLayout.

Bug: 198361315
Test: manual
      1. Launch Settings app by a Settings shortcut widget.
      2. Move Settings app to background.
      3. Click Settings shortcut widget again.
         Observe if SettingsHomepageActivity re-creates.
Change-Id: I4d71330f6a1760768ba4443e192f66b0a2cbb6bf