glsl/linker: Avoid buffer over-run in parcel_out_uniform_storage::visit_field

When too may uniforms are used, the error will be caught in
check_resources (src/glsl/linker.cpp).

NOTE: This is a candidate for the 8.0 branch.

Signed-off-by: Stéphane Marchesin <marcheu@chromium.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Tested-by: Benoit Jacob <bjacob@mozilla.com>

src/glsl/link_uniforms.cpp

@@ -313,7 +313,7 @@ private:
 	 const gl_texture_index target = base_type->sampler_index();
 	 const unsigned shadow = base_type->sampler_shadow;
 	 for (unsigned i = this->uniforms[id].sampler
-		 ; i < this->next_sampler
+		 ; i < MIN2(this->next_sampler, MAX_SAMPLERS)
 		 ; i++) {
 	    this->targets[i] = target;
 	    this->shader_samplers_used |= 1U << i;