Add minimum bandwidth config for showing LTE+ data icon

Only show the LTE+ icon if the combined channel bandwidth is greater
than the valued defined. By default, the value is 20 MHz, and if there
is no limit then the value should be 0.

Test: atest NetworkTypeControllerTest
Bug: 160873305
Change-Id: I4068860c5798f921fc198c095ba9b8f84ae5663b