init: switch from /dev/keychord to /dev/input/

Replace deprecated /dev/keychord driver with /dev/input/ interface.
Will restrict which nodes are active and relevant, and try to mask
out any unreferenced inputs with EVIOCSMASK if available.

Test: manual, boot, check registered chord works
Bug: 64114943
Change-Id: I2bbf84a6e472d720f02282e10d56795b75ac62d1