misc: tps6594-pfsm: Add NULL pointer check in tps6594_pfsm_probe()

In the Linux kernel, the following vulnerability has been resolved: misc: tps6594-pfsm: Add NULL pointer check in tps6594_pfsm_probe() The returned value, pfsm->miscdev.name, from devm_kasprintf() could be NULL. A pointer check is added to prevent potential NULL pointer dereference. This is similar to the fix in commit 3027e7b15b02 ("ice: Fix some null pointer dereference issues in ice_ptp.c"). This issue is found by our static analysis tool.