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.