selftests: riscv: verify ptrace rejects invalid vector csr inputs

selftests: riscv: verify ptrace rejects invalid vector csr inputs

Add a test to v_ptrace test suite to verify that ptrace rejects the
invalid input combinations of vector csr registers. Use kselftest
fixture variants to create multiple invalid inputs for the test.

Signed-off-by: Sergey Matyukevich <geomatsi@gmail.com>
Tested-by: Andy Chiu <andybnac@gmail.com>
Link: https://patch.msgid.link/20251214163537.1054292-9-geomatsi@gmail.com
[pjw@kernel.org: cleaned up some checkpatch issues]
Signed-off-by: Paul Walmsley <pjw@kernel.org>