Input: wm97xx - enable sub-drivers by default

Currently the support for each WM97xx touchscreen model is compiled out
by default, meaning that the default configuration when the driver is
built is for it to support no hardware.  This is suboptimal and leads to
problems like distribution kernels shipping a non-functional driver.

Change the default to support all controllers and update the help text
to reflect this.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>