Staging: HTC Dream: Cleanup Dream touchscreen driver

This is first part of touchscreen cleanups. I did not remove
earlysuspend functionality for now (to help Google merge the changes).

I mainly introduced helpers to reduce code duplication, and split huge
functions into smaller ones.
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>