ARC: [mm] optimise VIPT dcache aliasing 2/x

Non-congruent SRC page in copy_user_page() is dcache clean in the end -
so record that fact, to avoid a subsequent extraneous flush.

Signed-off-by: Vineet Gupta <[e-mail]>

arch/arc/mm/cache_arc700.c

···
 	 */
 	if (clean_src_k_mappings) {
 		__flush_dcache_page(kfrom, kfrom);
+		clear_bit(PG_arch_1, &from->flags);
 	} else {
 		set_bit(PG_arch_1, &from->flags);
 	}