staging: r8188eu: the MCS_rate_2R array is not used

The MCS_rate_2R array is not used in the r8188eu driver. Remove it.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220322202439.157999-3-martin@kaiser.cx


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