PM / docs: Drop confusing kernel-doc references from infrastructure.rst

The references to drivers/base/power/main.c and
drivers/acpi/scan.c from Documentation/driver-api/infrastructure.rst
are confusing.  They both cause descriptions of functions that are
not relevant to device drivers at all to be generated and none of
them is sufficient to cover the API in a meaningful way.

Drop them for now.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Jonathan Corbet <corbet@lwn.net>