staging: rtl8723bs: os_dep: modified return type of function rtw_suspend_wow() to void

Changed return type of function rtw_suspend_wow() to void.
The function always return _SUCCESS and the value is never
checked in the calling function.

Resolves coccicheck Unneeded variable "ret" warning.

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