vga_switcheroo: Use VGA_SWITCHEROO_UNKNOWN_ID instead of -1

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2 files changed