Keyguard: Add config to control whether show cancel button

By current design, when both the two SIM PINs are set, it can cancel
the first one, but have to enter the second SIM PIN code.

According to some carrier's requirement, it shouldn't show cancel
button, as it can't cancel both the two SIM PINs.
Add config to control whether show cancel button.

CRs-Fixed: 640259

Change-Id: I7b825086c5a38789cb23af15baf07c452401a853