Input: ep93xx_keypad - fix handling of platform_get_irq() error

Input: ep93xx_keypad - fix handling of platform_get_irq() error

[ Upstream commit 7d50f6656dacf085a00beeedbc48b19a37d17881 ]

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

Fixes: 60214f058f44 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>