[Intel-gfx] v4.9+ stable backport request

[Jani Nikula]

Stable team, please backport upstream commits

665788572c64 ("drm/i915/vbt: don't propagate errors from intel_bios_init()")
bb1d132935c2 ("drm/i915/vbt: split out defaults that are set when there is no VBT")

to stable kernels v4.9+. The first is a small refactor that makes the
actual fix in second easier and apply cleanly.

References: http://mid.mail-archive.com/CAD8Lp45zcVDAAshmiBbi3VZ-Zk=bCSBwP0Qw0QL8ibnDO-CECQ@mail.gmail.com
Fixes: 0ce140d45a83 ("drm/i915: Clean up DDI DDC/AUX CH sanitation")
Tested-by: Daniel Drake <drake at endlessm.com>
Cc: <stable at vger.kernel.org> # v4.9+

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center