staging: r8188eu: remove the private "test" ioctl

Remove the private "test" ioctl. It copies data from user space,
this data is not used.

We can now remove a number of NULL entries at the end of the private
ioctl list.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211226212535.197989-10-martin@kaiser.cx


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