drm/amd/display: Correct logic check error for fastboot

drm/amd/display: Correct logic check error for fastboot

[Why]
Fix fastboot broken in driver.
This is caused by an open source backport change 7495962c.

from the comment, the intended check is to disable fastboot
for pre-DCN10. but the logic check is reversed, and causes
fastboot to be disabled on all DCN10 and after.

fastboot is for driver trying to pick up bios used hw setting
and bypass reprogramming the hw if dc_validate_boot_timing()
condition meets.

Fixes: 7495962cbceb ("drm/amd/display: Disable fastboot on DCE 6 too")
Cc: stable@vger.kernel.org
Reviewed-by: Mario Limonciello <Mario.Limonciello@amd.com>
Reviewed-by: Ovidiu Bunea <ovidiu.bunea@amd.com>
Signed-off-by: Charlene Liu <Charlene.Liu@amd.com>
Signed-off-by: Ray Wu <ray.wu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>