remoteproc: qcom: q6v5: Fix potential null-ptr-deref in q6v5_wcss_init_mmio()

In the Linux kernel, the following vulnerability has been resolved:

remoteproc: qcom: q6v5: Fix potential null-ptr-deref in q6v5_wcss_init_mmio()

q6v5_wcss_init_mmio() will call platform_get_resource_byname() that may

fail and return NULL. devm_ioremap() will use res->start as input, which

may causes null-ptr-deref. Check the ret value of

platform_get_resource_byname() to avoid the null-ptr-deref.