use the correct name for the Button_Jack keylayout file

http://review.cyanogenmod.org/31970 renamed this to Button_Jack,
which wasn't changed when we switched to the new kernel for 4.2

It is now identified as "msm8960-snd-card Button Jack", and now with
config_useDevInputEventForAudioJack enabled, it works. :)

Change-Id: I35344d2ad0bcdafd64b7a18ced8f7afb6c63c8c6