Input: sun4i-ps2 - 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: e443631d ("Input: serio - add support for Alwinner A10/A20 PS/2 controller")
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20200828145744.3636-4-krzk@kernel.org


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