ASoC: cs35l36: Fix an IS_ERR() vs NULL checking bug

The irq_get_irq_data() function doesn't return error pointers, it
returns NULL.

Fixes: 6ba9dd6c ("ASoC: cs35l36: Add support for Cirrus CS35L36 Amplifier")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>