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: 7d2a5f9a ("ASoC: rt700: add rt700 codec driver")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200115143027.94364-1-weiyongjun1@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>