x86, olpc: Add comment about implicit optimization barrier

Signed-off-by: Andres Salomon <dilinger@queued.net>
Cc: H. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <20100618174653.7755a39a@dev.queued.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/olpc_ofw.c

@@ -35,6 +35,8 @@ void __init setup_olpc_ofw_pgd(void)
 
 	/* install OFW's PDE permanently into the kernel's pgtable */
 	set_pgd(&swapper_pg_dir[OLPC_OFW_PDE_NR], *ofw_pde);
+	/* implicit optimization barrier here due to uninline function return */
+
 	early_iounmap(base, sizeof(olpc_ofw_pgd) * PTRS_PER_PGD);
 }