staging: r8188eu: remove unused externl variables

Remove a group of external variables which are not used in
osdep_service.h or in the files where osdep_service.h is included.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220115165536.231210-2-martin@kaiser.cx


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