.clang-format: Add default clang-format configuration

[maribu]

Contribution description

This adds a clang-format configuration based on the Linux Kernel configuration and modified to better match RIOT's coding convention.

Testing procedure

Automatic formatting using clang-format should now match RIOT's coding convention relatively closely. Aligning bitmasks is still a pain point, though. I think this is not yet possible to configure, but something that we don't have too often. E.g. the following would still not work

/* good */
   FOO_REG = FOO_REG_VAL1
           | FOO_REG_VAL2
           | FOO_REG_VAL3;

/* bad (but sadly currently generated by clang-format) */
   FOO_REG = FOO_REG_VAL1 |
       FOO_REG_VAL2 | FOO_REG_VAL3;

Issues/PRs references

None

[maribu]

Would be interesting to know whether this would result (except for bitmasks) in correctly formatted code when using VS code.

[riot-ci]

Murdock results

✔️ PASSED

325c3a4 fixup! .clang-format: Add default clang-format configuration

Success	Failures	Total	Runtime
10197	0	10197	17m:30s

Artifacts

• Documentation preview