drm/i915/display: Force the state compute phase once to enable PSR

Recent improvements in the state tracking in i915 caused PSR to not be
enabled when reusing firmware/BIOS modeset, this is due to all initial
commits returning ealier in intel_atomic_check() as needs_modeset()
is always false.

To fix that here forcing the state compute phase in CRTC that is
driving the eDP that supports PSR once. Enable or disable PSR do not
require a fullmodeset, so user will still experience glitch free boot
process plus the power savings that PSR brings.

It was tried to set mode_changed in intel_initial_commit() but at
this point the connectors are not registered causing a crash when
computing encoder state.

v2:
- removed function return
- change arguments to match intel_hdcp_atomic_check

v3:
- replaced drm includes in intel_psr.h by forward declaration(Jani)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112253
Reported-by:  <s.zharkoff@gmail.com>
Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200106152128.195171-1-jose.souza@intel.com