ASoC: core: Fix Null-point-dereference in fmt_single_name()

Check the return value of devm_kstrdup() in case of
Null-point-dereference.

Fixes: 45dd9943

 ("ASoC: core: remove artificial component and DAI name constraint")
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Link: https://lore.kernel.org/r/20210524024941.159952-1-wangkefeng.wang@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>