staging: r8188eu: check for initiator vs recipient

For an incoming delba message, the code checks if the delba was sent by
the data initiator or by the data recipient.

Rewrite this check using the ieee80211 helpers, making the code easier to
understand.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220514164740.282552-7-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>