drm/radeon: add a quirk for Toshiba Satellite L20-183

Fixes resume from suspend.

bug: https://bugzilla.kernel.org/show_bug.cgi?id=196121
Reported-by: Przemek <soprwa@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org