i965: Add buffer sizes to perf debug of fast clears

i965: Add buffer sizes to perf debug of fast clears

When we cannot do the optimized fast clear it's important to know the buffer
size since a small buffer will have much less performance impact.

A follow-on patch could restrict printing the message to only certain sizes.

Example:
Failed to fast clear 1400x1056 depth because of scissors.  Possible 5% performance win if avoided.

Recommended-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>