Input: stmpe-keyboard - switch to using managed resources

This patch frees stmpe-keyboard driver from burden of freeing resources :)
devm_* derivatives of multiple routines are used while allocating resources,
which would be freed automatically by kernel.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>