staging: r8188eu: remove the private ioctl "get sensitivity"

Remove the private ioctl "get sensitivity", it is mapped to an empty
function.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211226212535.197989-3-martin@kaiser.cx


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