ASoC: rt715: fix return value check in rt715_sdw_probe()

In case of error, the function devm_regmap_init() returns ERR_PTR() and
never returns NULL. The NULL test in the return value check should be
replaced with IS_ERR().

Fixes: d1ede064 ("ASoC: rt715: add RT715 codec driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200117024149.75515-1-weiyongjun1@huawei.com


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