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.