Staging: rtl8723bs: Change values to standard error codes in functions

Change values for standard error codes in functions rtw_init_cmd_priv and
rtw_init_evt_priv, as _SUCCESS should be 0 and _FAIL should be -ENOMEM.
Also, change the values in corresponding call sites of the functions.

Signed-off-by: Madhumitha Prabakaran <madhumithabiw@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>