input: touchscreen: hxchipset: register the input device

Split the initialization function into two parts, one is for the driver
probe, another is for the deferred hw driver initialization. And the input
device will be registered as soon as possible.

Change-Id: I719ca348fc7a9d460ef91c0ea26d79e5b42384ac
Signed-off-by: Fei Mao <feim1@codeaurora.org>