powerpc/ptdump: Fix display of RW pages on FSL_BOOK3E

On FSL_BOOK3E, _PAGE_RW is defined with two bits, one for user and one
for supervisor. As soon as one of the two bits is set, the page has
to be display as RW. But the way it is implemented today requires both
bits to be set in order to display it as RW.

Instead of display RW when _PAGE_RW bits are set and R otherwise,
reverse the logic and display R when _PAGE_RW bits are all 0 and
RW otherwise.

This change has no impact on other platforms as _PAGE_RW is a single
bit on all of them.

Fixes: 8eb07b18 ("powerpc/mm: Dump linux pagetables")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0c33b96317811edf691e81698aaee8fa45ec3449.1656427391.git.christophe.leroy@csgroup.eu

arch/powerpc/mm/ptdump/shared.c

@@ -17,9 +17,9 @@ static const struct flag_info flag_array[] = {
 		.clear	= "    ",
 	}, {
 		.mask	= _PAGE_RW,
-		.val	= _PAGE_RW,
-		.set	= "rw",
-		.clear	= "r ",
+		.val	= 0,
+		.set	= "r ",
+		.clear	= "rw",
 	}, {
 		.mask	= _PAGE_EXEC,
 		.val	= _PAGE_EXEC,