staging: rtl8723bs: delete rtw_setdatarate_cmd

Remove function rtw_setdatarate_cmd because it is not used.

Signed-off-by: Nam Cao <namcaov@gmail.com>
Link: https://lore.kernel.org/r/bfc4c5c9aec8b026fd3cf092354d508881d790fc.1662111798.git.namcaov@gmail.com


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