selftests: can: Import tst-filter from can-tests

Tests for the can subsystem have been in the can-tests repository[1] so
far. Start moving the tests to kernel selftests by importing the current
tst-filter test. The test is now named test_raw_filter and is substantially
updated to be more aligned with the kernel selftests, follow the coding
style, and simplify the validation of received CAN frames. We also include
documentation of the test design. The test verifies that the single filters
on raw CAN sockets work as expected.

We intend to import more tests from can-tests and add additional test cases
in the future. The goal of moving the CAN selftests into the tree is to
align the tests more closely with the kernel, improve testing of CAN in
general, and to simplify running the tests automatically in the various
kernel CI systems.

[1]: https://github.com/linux-can/can-tests



Signed-off-by: Felix Maurer <fmaurer@redhat.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://patch.msgid.link/87d289f333cba7bbcc9d69173ea1c320e4b5c3b8.1747833283.git.fmaurer@redhat.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>