ANDROID: input: keychord: Fix for a memory leak in keychord.

Fixes a steady memory leak in the keychord release code. A close of
the keychord device will leak 1 keychord structure. Easily
reproducible by a simple program that does an open()->write()->close()
of the keychord device.

Bug: 64483974
Change-Id: I1fa402c666cffb00b8cfd6379d9fe47a0989152c
Signed-off-by: Mohan Srinivasan <srmohan@google.com>