staging: r8188eu: remove intermediate pframe pointer

The pframe pointer in on_action_public is used only in the definition of
frame_body, which points to the payload of an incoming action frame.

We can use mgmt to locate the action payload and remove the pframe
pointer.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/20221230175326.90617-4-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>