drm/i915: Dump error capture to kernel log

drm/i915: Dump error capture to kernel log

This is useful for getting debug information out in certain
situations, such as failing kernel selftests and CI runs that don't
log error captures. It is especially useful for things like retrieving
GuC logs as GuC operation can't be tracked by adding printk or ftrace
entries.

v2: Add CONFIG_DRM_I915_DEBUG_GEM wrapper (review feedback by Rodrigo).

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230418181744.3251240-2-John.C.Harrison@Intel.com