drm/i915/guc: Increase GuC log size for CONFIG_DEBUG_GEM

Lots of testing is done with the DEBUG_GEM config option enabled but
not the DEBUG_GUC option. That means we only get teeny-tiny GuC logs
which are not hugely useful. Enabling full DEBUG_GUC also spews lots
of other detailed output that is not generally desired. However,
bigger GuC logs are extremely useful for almost any regression debug.
So enable bigger logs for DEBUG_GEM builds as well.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211211065859.2248188-3-John.C.Harrison@Intel.com