static_call: Replace pointless WARN_ON() in static_call_module_notify()

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

static_call: Replace pointless WARN_ON() in static_call_module_notify()

static_call_module_notify() triggers a WARN_ON(), when memory allocation

fails in __static_call_add_module().

That's not really justified, because the failure case must be correctly

handled by the well known call chain and the error code is passed

through to the initiating userspace application.

A memory allocation fail is not a fatal problem, but the WARN_ON() takes

the machine out when panic_on_warn is set.

Replace it with a pr_warn().