Replace the previous approach to force compute the initial PSR state
after i915 take over from firmware by the better and recently added
initial_fastset_check() hook.

Cc: Imre Deak <imre.deak@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201102221048.104294-1-jose.souza@intel.com