i965: Don't allocate an MCS for 16x MSAA and width > 8192.

i965: Don't allocate an MCS for 16x MSAA and width > 8192.

The hardware doesn't support this, and isl_surf_get_mcs_surf will fail.

I feel a bit bad replicating this logic, but we want to decide up front.

This fixes the following test when run with --deqp-surface-width=16384:
- GTF-GL46.gtf30.GL3Tests.framebuffer_blit.framebuffer_blit_error_blitframebuffer_multisampled_framebuffers_different_sample_count

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>