powerpc/ptdump: Only enable PPC_CHECK_WX with STRICT_KERNEL_RWX

powerpc/ptdump: Only enable PPC_CHECK_WX with STRICT_KERNEL_RWX

commit f509247b08f2dcf7754d9ed85ad69a7972aa132b upstream.

ptdump_check_wx() is called from mark_rodata_ro() which only exists
when CONFIG_STRICT_KERNEL_RWX is selected.

Fixes: 453d87f6a8ae ("powerpc/mm: Warn if W+X pages found on boot")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/922d4939c735c6b52b4137838bcc066fffd4fc33.1578989545.git.christophe.leroy@c-s.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>