Revert "i965/wm: use proper API buffer size for the surfaces."

Revert "i965/wm: use proper API buffer size for the surfaces."

This reverts commit 8cf2e892fca20c4776b4a07c39918343cb2d4e0e. It's
entirely bogus to attempt to store anything about the binding in the
buffer object itself, which might be bound any number of times.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Cc: Marta Lofstedt <marta.lofstedt@intel.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>