drm/cmdline-parser: Merge negative tests

Negative tests can be expressed as a single parameterized test case,
which highlights that we're following the same test logic (passing
invalid cmdline and expecting drm_mode_parse_command_line_for_connector
to fail), which improves readability.

v2: s/negative/invalid to be consistent with other testcases in DRM

Signed-off-by: Michał Winiarski <[email protected]>
Reviewed-by: Maíra Canal <[email protected]>
Signed-off-by: Maíra Canal <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: mwiniars