This patch intends to remove redundant computations on combined
interface block counts in ValidateGraphicsInterfaceBlocks.

In this patch, we compute and check the number of combined interface
blocks by the result of ValidateInterfaceBlocksCount directly instead
of re-compute it, and if the check on max combined interface blocks
failed, Program::link() can early return without entering
ValidateGraphicsInterfaceBlocks.

BUG=angleproject:2345

Change-Id: I7573f7c645993b4d75230a8471203a305127f2a3
Reviewed-on: https://chromium-review.googlesource.com/1031852Reviewed-by: Jiajia Qin <jiajia.qin@intel.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>