Revert "drm/amdkfd: Unify gfx9/gfx10 context save area layouts"

This reverts commit 0a5baee4.

The change introduced a regression on some chips. Reverting until
a proper solution can be found.

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>