staging: r8188eu: clean up error handling in rtw_start_drv_threads()

Convert the error handling in the function rtw_start_drv_threads() to
the common logic used in the kernel. Another step to get rid of _FAIL
and _SUCCESS which uses inverted logic.

Signed-off-by: Michael Straube <straube.linux@gmail.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/20221106133443.8872-1-straube.linux@gmail.com


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