Keyguard: Add option to scramble pin layout when unlocking (2/2).

Adapted to Lineage SDK and squashed with the following changes:

  From: Adnan Begovic <adnan@cyngn.com>
  Date: Wed, 05 Aug 2015 10:40:41 -0700

      Keyguard: Don't disable visibility when scrambling pin.

        Otherwise the first numbers text is flipped to invisible
        even though it shouldn't be.

      Change-Id: Ia2b80d594e7f11af7a60a85bdb4ea9909d0ac20b

  From: Adnan Begovic <adnan@cyngn.com>
  Date: Wed, 05 Aug 2015 16:21:27 -0700

      Keyguard: Fix scramblepin logic.

      Change-Id: I71e6d26e853fa7bfaeea4b3256902881ac7f74fc

Original Change-Id: Ibe8611eb0b8a5bd9275bc96682d2cbafaa37d8f5
Change-Id: I6716b1c76b69d51bd1457ce07de2274541fca1e8