ASoC: mt6359: fix tests for platform_get_irq() failure

The platform_get_irq() returns negative error codes.  It can't actually
return zero, but if it did that should be treated as success.

Fixes: eef07b9e

 ("ASoC: mediatek: mt6359: add MT6359 accdet jack driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/YvThhr86N3qQM2EO@kili


Signed-off-by: Mark Brown <broonie@kernel.org>