input: jdi-bu21150: add sysfs entry to expose touch AFE information

Add sysfs entry to expose touch AFE specific information to userspace
software. The information is passed in the form of strings which are
composed of information read from device tree.

Change-Id: Id8dbbf42fdc6318534c4533e4959d07aec3c55d2
Signed-off-by: Chun Zhang <chunz@codeaurora.org>