ASoC: pxa: fix null-pointer dereference in filter()

ASoC: pxa: fix null-pointer dereference in filter()

[ Upstream commit e963afd04463c3ed3400fd7fd75cb720c4c8e63e ]

kasprintf() would return NULL pointer when kmalloc() fail to allocate.
Need to check the return pointer before calling strcmp().

Fixes: ec2d347c4f37 ("ASoC: mmp: add audio dma support")
Signed-off-by: Zeng Heng <zengheng4@huawei.com>
Link: https://lore.kernel.org/r/20221114085629.1910435-1-zengheng4@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>