staging: r8723au: Add missing initialization of change_inx in sort algorithm

drivers/staging/rtl8723au/core/rtw_wlan_util.c: In function ‘WMMOnAssocRsp23a’:
drivers/staging/rtl8723au/core/rtw_wlan_util.c:684: warning: ‘change_inx’ may be used uninitialized in this function

Depending on the uninitialized data on the stack, the array may not be
sorted correctly.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>