Input: ep93xx_keypad - annotate suspend/resume as __maybe_unused

Instead of guarding suspend/resume methods with #ifdef CONFIG_PM
let's mark them as __maybe_unused as this allows better compile
coverage.

Acked-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Link: https://lore.kernel.org/r/20211012013735.3523140-1-dmitry.torokhov@gmail.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>