Revert "radeonsi: don't emit PKT3_CONTEXT_CONTROL on amdgpu"

This reverts commit 5a2e65be.

Even though CONTEXT_CONTROL is emitted by the kernel, CONTEXT_CONTROL
still needs to be emitted by the UMD, or else the driver will hang

Cc: 19.2 <mesa-stable@lists.freedesktop.org>
Signed-off-by: Thong Thai <thong.thai@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 2a3a5604)