staging: rtl8723bs: Remove unreachable Code in core/rtw_cmd.c

The `case INTEl_WIDI_WK_CID`-Statement in Function `u8 rtw_drvextra_cmd_hdl`
wouldn't be used because of CONFIG_INTEL_WIDI.

Signed-off-by: Emanuel Bennici <benniciemanuel78@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>