staging: r8188eu: get bssid from mgmt struct

staging: r8188eu: get bssid from mgmt struct

For management frames, Addr3 is the BSSID. Read it from the mgmt
structure instead of calling GetAddr3Ptr.

The pframe variable is now unused and can be removed.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Acked-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20221015152440.232281-6-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>