Revert "drm/i915: mark all device info struct with __initconst"

This reverts commit 5b54eddd.

 Conflicts:
	drivers/gpu/drm/i915/i915_pci.c

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104805


Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: 5b54eddd ("drm/i915: mark all device info struct with __initconst")
Link: https://patchwork.freedesktop.org/patch/msgid/20180129083346.29173-1-lionel.g.landwerlin@intel.com