remoteproc: pru: Fix potential NULL pointer dereference in pru_rproc_set_ctable()

In the Linux kernel, the following vulnerability has been resolved: remoteproc: pru: Fix potential NULL pointer dereference in pru_rproc_set_ctable() pru_rproc_set_ctable() accessed rproc->priv before the IS_ERR_OR_NULL check, which could lead to a null pointer dereference. Move the pru assignment, ensuring we never dereference a NULL rproc pointer.