drm/i915/bdw: sseu: Fix sseu status parsing

Currently when checking for fused off EUs we may ignore the EU count in
an enabled slice if there is any disabled slice preceding the enabled
one (with a lower slice ID). Perhaps this can't happen in reality, but
there is no reason to have this assumption built-in, the code is clearer
without it.

Reviewed-by: Robert Bragg <robert@sixbynine.org>
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>
Tested-by: Ben Widawsky <benjamin.widawsky@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1472659987-10417-8-git-send-email-imre.deak@intel.com