libsysdecode: Add regression tests for sysdecode_cap_rights(3)

[emaste]

lib/libsysdecode/tests/sysdecode_test.c

101

I wonder about the naming, having not spent much time looking at ATF C tests before, it wasn't immediately obvious that sysdecode_cap_rights is the library routine and sysdecode_cap_rights_check is our test function. If this is the usual approach for ATF that's fine, otherwise maybe put check before the fn name?

[markj]

lib/libsysdecode/tests/sysdecode_test.c

101

Yeah, better to avoid the libsysdecode namespace. There's a bunch of redundancy here too that I'll clean up.

[markj]

Simplify, improve naming.

[emaste]

yeah, much clearer to me

lib/libsysdecode/tests/sysdecode_test.c

133

I might put the cap_rights_clear call by itself and just pass rights, feels slightly odd to set up the rights only partially in the check_sysdecode_cap_rights call

[markj]

apply Ed's suggestion, add another test