staging: greybus: loopback: fix a spelling error.

Successed -> succeeded.

Signed-off-by: Till Varoquaux <till.varoquaux@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/r/20200518051314.1785567-1-till.varoquaux@gmail.com


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