drm/i915/skl: Refuse to load outdated dmc firmware

drm/i915/skl: Refuse to load outdated dmc firmware

There is known issue on GT interrupt delivery with DC6 and
firmwares <1.21. There is a suspicion that this causes
spurious gpu hangs on driver init and with some workloads,
as upgrading the firmware to 1.21 makes these problems
disappear.

As of now the current version included in distribution
firmware packages is very like to be 1.19. Play it safe and
refuse to load a firmware version that may affect gpu
side stability.

With < 1.23 there is a palette and dmc ram corruption issue
so blacklist anything below that.

v2: Refuse to load fw instead of notifying the user
v3: Rebase on header version changes
v4: Refuse to load anything less than 1.23
v5: Give enough information for user for finding correct fw (Chris)
v6: better url and formatting (Chris)
v7: move error log for each fail path (Mika)
    bail out earlier in load path (Imre)
v8: Fix the version check (Imre)

Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
References: https://01.org/linuxgraphics/downloads/skldmcver121
References: https://01.org/linuxgraphics/downloads/skylake-dmc-1.23
Testcase: igt/gem_exec_nop
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1446220336-32392-1-git-send-email-mika.kuoppala@intel.com
Tested-by: Daniel Stone <daniels@collabora.com> # SKL
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>