Input: lpc32xx-keys - switch to using managed resources

This change switches to using devm_* managed resources APIs to
request the resources in probe to simplify probe error path and
module unloading.

Signed-off-by: Pramod Gurav <pramod.gurav@smartplayin.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>