drm/i915/debugfs: add rcs topology entry

While the end goal is to make this information available to userspace
through a new ioctl, there is no reason we can't display it in a human
readable fashion through debugfs.

slice0: 3 subslice(s) (0x7):
	subslice0: 8 EUs (0xff)
	subslice1: 8 EUs (0xff)
	subslice2: 8 EUs (0xff)
	subslice3: 0 EUs (0x0)
slice1: 3 subslice(s) (0x7):
	subslice0: 8 EUs (0xff)
	subslice1: 8 EUs (0xff)
	subslice2: 8 EUs (0xff)
	subslice3: 0 EUs (0x0)
slice2: 3 subslice(s) (0x7):
	subslice0: 8 EUs (0xff)
	subslice1: 8 EUs (0xff)
	subslice2: 8 EUs (0xff)
	subslice3: 0 EUs (0x0)

v2: Reformat debugfs printing (Tvrtko)
    Use the new EU mask helper (Tvrtko)

v3: Move printing code to intel_device_info.c to be shared with error
    state (Michal)

v4: Bump u8 to u16 when using sseu_get_eus() (Lionel)

Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
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/20180306122857.27317-4-lionel.g.landwerlin@intel.com