Input: ep93xx_keypad - fix handling of platform_get_irq() error

platform_get_irq() returns -ERRNO on error.  In such case comparison
to 0 would pass the check.

Fixes: 60214f05 ("Input: ep93xx_keypad - update driver to new core support")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200828145744.3636-1-krzk@kernel.org


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