[Mesa-stable] [cherry-pick] nvc0: increase alignment to 256 for texture buffers on fermi

[Ilia Mirkin]

Please cherry-pick commit 32dd8d59b6d1b6828e16e854d589d0f04536da14
into stable (probably appropriate for both 13.0 and 17.0). Roy since
reported that this makes the invalid data errors disappear for him.
(Although he still saw some bad rendering, but that is likely a
separate issue.)

>From 32dd8d59b6d1b6828e16e854d589d0f04536da14 Mon Sep 17 00:00:00 2001
From: Ilia Mirkin <imirkin at alum.mit.edu>
Date: Wed, 1 Mar 2017 11:09:30 -0500
Subject: nvc0: increase alignment to 256 for texture buffers on fermi

When binding as textures, the alignment can be 16. However when binding
as an image, the address has to be aligned to 256. (Also when binding as
an RT, but that can't happen with GL or current gallium APIs.)

Reported-by: Roy Spliet <nouveau at spliet.org>
Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
Acked-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>