staging: r8188eu: use ieee80211 define for management frame type

Replace the driver-internal define for management frame type with
IEEE80211_FTYPE_MGMT.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220227164147.1168847-2-martin@kaiser.cx


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