The BlankCrtc table in some DCE8 boards has some
logic shortcuts for the vbios when this bit is set.
Clear it for driver use.

v2: fix typo

Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=73420Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org