staging: rtl8723bs: os_dep: Change return type of function rtw_suspend_normal() to void

Coccicheck issues Unneeded variable "ret" warning.
The return value of function rtw_suspend_normal() is set to _SUCCESS.
The return value is never never checked by the calling function.
Modified return type to void to remove the coccicheck warning..

Signed-off-by: Shobhit Kukreti <shobhitkukreti@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>