drm/i915: Drop redundant checks to update PSR state

All of this checks are redudant and can be removed as the if bellow
already takes care when there is no changes in the state.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190308000050.6226-7-jose.souza@intel.com