Staging: HTC Dream: touchscreen: more cleanups

This separates coefficient computation into separate function, so that
main probe does not have 1001 variables, and is of a more reasonable
size.

Signed-off-by: Pavel Machek <pavel@ucw.cz>
Cc: Arve Hjønnevåg <arve@android.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>