A divisor >= 256 used to trigger an assert on the D3D11 backend since
it couldn't fit into the input layout cache. Increase the space
reserved for the divisor in the input layout cache to make sure that
the correct input layout will get used and to fix the assert.

BUG=angleproject:2832
TEST=angle_end2end_tests

Change-Id: I34eead6c4e8c4fea379bbafc8670b4e32a5b633b
Reviewed-on: https://chromium-review.googlesource.com/1236293Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>