drm/amdgpu: revert "enable gfxoff in non-sriov and stutter mode by default"

This is still completely breaking my Raven system.

This reverts commit cdf2f910fa969adca1b0e3ad2b487821233dc038.

Revert until we sort out the sbios and firmware combinations that work
correctly.

bug: https://bugs.freedesktop.org/show_bug.cgi?id=108606


Cc: stable@vger.kernel.org # v4.19

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>