staging:rtl8723au: core: Fix checkpatch warning

This is a patch to the rtw_cmd.c file that fixes following
Warning by introducing temporary structure.

WARNING: line over 80 characters

Signed-off-by: Sanjeev Sharma <Sanjeev_Sharma@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>