powerpc: Fix ioremap_flags() with book3e pte definition

powerpc: Fix ioremap_flags() with book3e pte definition

commit 55052eeca6d71d76f7c3f156c0501814d8e5e6d3 upstream.

We can't just clear the user read permission in book3e pte, because
that will also clear supervisor read permission.  This surely isn't
desired.  Fix the problem by adding the supervisor read back.

BenH: Slightly simplified the ifdef and applied to ppc64 too

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>