platform/x86/amd/pmf: Ensure mutexes are initialized before use

As soon as the first handler or sysfs file is registered
the mutex may get used.

Move the initialization to before any handler registration /
sysfs file creation.

Likewise move the destruction of the mutex to after all
the de-initialization is done.

Fixes: da5ce22d

 ("platform/x86/amd/pmf: Add support for PMF core layer")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20230130132554.696025-1-hdegoede@redhat.com