staging: r8188eu: use hdr->frame_control instead of fc

We can remove the fc variable in update_recvframe_phyinfo_88e and use
hdr->frame_control instead.

Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20221031205412.124871-3-martin@kaiser.cx


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