drm/i915: return -EIO on lmem setup failure

Caller of setup_lmem() ignores -ENODEV but failing
to setup lmem on dGPU isn't ignorable error.

Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220511153746.14142-1-nirmoy.das@intel.com