drm/amdgpu/psp: don't free PSP buffers on suspend

We can reuse the same buffers on resume.

v2: squash in S4 fix from Shikai

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/2213


Reviewed-by: Christian König <christian.koenig@amd.com>
Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org