systemui: don't use SIM display name if there isn't available info

If there is no SIM info, then don't try to use SIM name.
Also don't try to process all the network info data to obtain a network name, if we
are able to extract it from SIM.

Change-Id: I9b4ab296b7647ebab50925b8614beb820d2c6ace
JIRA: BUGDUMP-1081990
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>