radv: bump minTexelBufferOffsetAlignment to 4

The spec has probably been misinterpreted during RADV bringup.

This fixes GPU hangs with dEQP-VK.binding_model.*offset_nonzero*.

Fixes: f4e499ec ("radv: add initial non-conformant radv vulkan driver")
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
(cherry picked from commit 030e67fa)