st/mesa: fix blit-based partial TexSubImage for 1D arrays

This fixes piglit spec/EXT_texture_array/render-1darray.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

src/mesa/state_tracker/st_cb_texture.c

@@ -719,6 +719,8 @@ st_TexSubImage(struct gl_context *ctx, GLuint dims,
 
    /* From now on, we need the gallium representation of dimensions. */
    if (gl_target == GL_TEXTURE_1D_ARRAY) {
+      zoffset = yoffset;
+      yoffset = 0;
       depth = height;
       height = 1;
    }