SystemUI: Remove unnecessary mobile data activity icon update

The unnecessary mobile data activity icon update causes activity
icon is 0 when mobile data is not actually used. As a result, data
icon will not show even if data connected.

As mobile data activity icon has updated in updateDataIcon, do not
update it again in refreshViews. Remove unnecessary mobile activity
indicator icon update.

Change-Id: Ib39c55a39a0623cc9a2d14508d487f86e3a0f82f
CRs-Fixed: 745386