drm/i915: store all subslice masks

Up to now, subslice mask was assumed to be uniform across slices. But
starting with Cannonlake, slices can be asymmetric (for example slice0
has different number of subslices as slice1+). This change stores all
subslices masks for all slices rather than having a single mask that
applies to all slices.

v2: Rework how we store total numbers in sseu_dev_info (Tvrtko)
    Fix CHV eu masks, was reading disabled as enabled (Tvrtko)
    Readability changes (Tvrtko)
    Add EU index helper (Tvrtko)

v3: Turn ALIGN(v, 8) / 8 into DIV_ROUND_UP(v, BITS_PER_BYTE) (Tvrtko)
    Reuse sseu_eu_idx() for setting eu_mask on CHV (Tvrtko)
    Reformat debug prints for subslices (Tvrtko)

v4: Change eu_mask helper into sseu_set_eus() (Tvrtko)

v5: With Haswell reporting masks & counts, bump sseu_*_eus() functions
    to use u16 (Lionel)

v6: Fix sseu_get_eus() for > 8 EUs per subslice (Lionel)

v7: Change debugfs enabels for number of subslices per slice, will
    need a small igt/pm_sseu change (Lionel)
    Drop subslice_total field from sseu_dev_info, rely on
    sseu_subslice_total() to recompute the value instead (Lionel)

v8: Remove unused function compute_subslice_total() (Lionel)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180306122857.27317-2-lionel.g.landwerlin@intel.com