staging: r8188eu: wifi_error_status is write-only

wifi_error_status in struct sreset_priv is set in a couple of places,
its value is never used.

Remove wifi_error_status itself, the defines for the possible values and
the sreset_set_wifi_error_status function.

Rewrite the if statement in usb_write_port_complete. For purb->status ==
-EPIPE or -EPROTO, nothing should be done.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211024180448.20624-3-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>