SystemUI: Fix "wifi icon overlaps mobile signal icon" issue

The mobile signal icon is not triangle in carrier style, so it's necessary
to insert a spacer between wifi icon and sim1 mobile signal icon.

Use the spacer if the signal style of sim1 is not default.

CRs-Fixed: 638161

Change-Id: Ifb842574721fbdcbc93d2c573cc9851ceb9ba35f