drm/i915/guc: Move defines with size of GuC logs to intel_guc_log.h

At this moment, we have defined GuC logs sizes in intel_guc_fwif.h, but
as these values are related directly to the GuC logs, and not to API of
GuC parameters, we should move these defines to intel_guc_log.h.

v2:
- change buffers size to more friendly (Michał Wajdeczko)
- remove GUC_LOG_SIZE define (Michał Wajdeczko)
v3:
- use SZ_* macros to define buffers sizes (Michał Wajdeczko)

Signed-off-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180605151330.9954-1-piotr.piorkowski@intel.com