ASoC: qdsp6: Fix an IS_ERR() vs NULL bug

The function gpr_alloc_port return ERR_PTR on errors, it doesn't return
null.

Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Link: https://lore.kernel.org/r/20211211065840.1221-1-linmq006@gmail.com


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