DataUsageSummary: fix mobile data usage display for GSM devices with no number

Some providers don't write phone number onto SIM card causing the
phone number check introduced in the partially reverted commit to fail.
Re-introduce the original check with the "or" condition.

This partially reverts commit 4c51b453.

Change-Id: I69a65a1a421dcdf168c3d0afeb7110cb97790034