llvmpipe: add multisample support to texture allocator.

This adds a sample stride field and allocates enough memory for
each sample storage. Hook up the sample_stride field to draw
and jit textures and images

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4122>

src/gallium/drivers/llvmpipe/lp_texture.c

@@ -76,6 +76,8 @@ llvmpipe_texture_layout(struct llvmpipe_screen *screen,
    unsigned depth = pt->depth0;
    uint64_t total_size = 0;
    unsigned layers = pt->array_size;
+   unsigned num_samples = util_res_sample_count(pt);
+
    /* XXX:
     * This alignment here (same for displaytarget) was added for the purpose of
     * ARB_map_buffer_alignment. I am not convinced it's needed for non-buffer
@@ -166,6 +168,9 @@ llvmpipe_texture_layout(struct llvmpipe_screen *screen,
       depth = u_minify(depth, 1);
    }
 
+   lpr->sample_stride = total_size;
+   total_size *= num_samples;
+
    if (allocate) {
       lpr->tex_data = align_malloc(total_size, mip_align);
       if (!lpr->tex_data) {