staging: r8188eu: remove psa, pda

Remove the psa, pda variables. They are set and read only once.
We can use the ieee80211 helpers directly.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220403165438.357728-10-martin@kaiser.cx


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