drm/i915: reorder if chain to have last gen first

Reorder if/else so we check for gen >= 11 first, similar to most of
other checks in the driver.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190404230426.15837-3-lucas.demarchi@intel.com