staging: r8188eu: remove enum _RTL8712_RF_MIMO_CONFIG_

The enum _RTL8712_RF_MIMO_CONFIG_ is not used, remove it.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20211009104419.8811-3-straube.linux@gmail.com


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