staging: r8188eu: read destination address from ieee80211_mgmt

For management frames, addr1 is the destination address (da). Read this
address from struct ieee80211_mgmt instead of calling a driver-specific
macro.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220508161451.115847-4-martin@kaiser.cx


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