staging: rtlwifi: SET_RATE_ID inline no arg reuse

The macro SET_RATE_ID is a definition in function
and undefined at end of function.
Make it as inline avoid the arg reuse for macro,
the name is changed in _rtl_rate_id, following the
same function pattern in the file.

Signed-off-by: Cristian Sicilia <sicilia.cristian@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>