staging: rtl8188eu: remove a couple of unused defines

Remove some defines which are not used by this driver.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20210620175301.14988-4-martin@kaiser.cx


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