Fix sloppy CAN_(EFF|RTR)_FLAG handling in can_filter.can_mask .

Fix sloppy CAN_(EFF|RTR)_FLAG handling in can_filter.can_mask .

Due to a wrong safety check in af_can.c it was not possible to filter
for SFF frames with a specific CAN identifier without getting the
same selected CAN identifier from a received EFF frame also.

This fix has a minimum impact on the CAN filter API as the 'sloppy'
handling is still a correct (and possibly wanted?) use-case.

Please update the can-utils (especially candump) whose filter definition
on the commandline made assumptions to correct the user input that are
probably unwanted now.

Thanks to Kurt van Dijck for pointing at this issue!

Signed-Off-by: Oliver Hartkopp <oliver@hartkopp.net>