drm/amdgpu: partial revert "remove ctx->lock" v2

drm/amdgpu: partial revert "remove ctx->lock" v2

This reverts commit 5385e13cbe8ee128ad0d00f14ee416c4931342a5.

We are missing some inter dependencies here so re-introduce the lock
until we have figured out what's missing. Just drop/retake it while
adding dependencies.

v2: still drop the lock while adding dependencies

Signed-off-by: Christian König <christian.koenig@amd.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> (v1)
Fixes: 5385e13cbe8e ("drm/amdgpu: remove ctx->lock")
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220419110633.166236-1-christian.koenig@amd.com