PM: Fix typo in label name s/Platofrm_finish/Platform_finish/

Although the same label name is used somewhere else in the file, this
particular label was consistently typoed in all of its uses.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>