PM / core: remove unneeded kallsyms include

The file was converted from print_fn_descriptor_symbol()
to %pF some time ago (c80cfb04 "vsprintf: use new
vsprintf symbolic function pointer format"). kallsyms does
not seem to be needed anymore.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>