staging: r8188eu: convert rtw_setdatarate_cmd to correct error semantics

staging: r8188eu: convert rtw_setdatarate_cmd to correct error semantics

Convert rtw_setdatarate_cmd function to use proper error return codes
rather than _SUCCESS and _FAIL, and a simpler 'return 0;' style. For now,
wrap rtw_enqueue_cmd call and return -EPERM if it fails, as converting
this function makes more sense later on due to its large number of callers.

Also change rtw_wx_set_rate function to pass through the proper error
code rather than just 0 or -1.

Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://lore.kernel.org/r/20221102003613.971-1-phil@philpotter.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>