staging: rtl8723bs: Change type of rtw_os_recv_resource_alloc()

Remove assignment of the return value of rtw_os_recv_resource_alloc as
this assignment at the call site is never used.
Remove return statement from rtw_os_recv_resource_alloc() as its return
variable is never used.
Change the type of the function to void.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>