staging: r8188eu: use mgmt to set the category

Use the mgmt structure in issue_action_BA to set the category of the
outgoing frame. Remove the rtw_set_fixed_ie call.

We can now use the define directly, the category variable can be removed.

rtw_set_fixed_ie increments pattrib->pktlen, we have to do this ourselves
now (until we use a proper way to calculate the packet length).

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220524090029.242584-7-martin@kaiser.cx


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