It is sometimes frustrating to use open_file_dma, because it has the hardcoded
behavior of always assuming O_CREAT. Sometimes this is not desirable, and it
would be nice to have the option not to do so.
Note that, by design, I am only including in the open_flags enum things that we
want the user of the API to control. Stuff like O_DIRECT should not be
optional, and therefore is not included in the visible interface.
Because of that I am changing the function signature to include a paramater
that specifies whether or not we should create the file if it does not exist.
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>