glsl: use bool literals instead of integers

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12674>

src/compiler/glsl/link_varyings.cpp

@@ -2173,7 +2173,7 @@ varying_matches::store_locations() const
    /* Check is location needs to be packed with lower_packed_varyings() or if
     * we can just use ARB_enhanced_layouts packing.
     */
-   bool pack_loc[MAX_VARYINGS_INCL_PATCH] = { 0 };
+   bool pack_loc[MAX_VARYINGS_INCL_PATCH] = {};
    const glsl_type *loc_type[MAX_VARYINGS_INCL_PATCH][4] = { {NULL, NULL} };
 
    for (unsigned i = 0; i < this->num_matches; i++) {