Input: pxa27x_keypad - switch to using managed resources

This change switches ithe driver to use devm_* APIs to allocate resources.
This helps to simplify failure path in probe function and module unloading
and does away with remove function.

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