Kconfig: Make STRICT_DEVMEM default-y on x86 and arm64

Distros have been shipping with CONFIG_STRICT_DEVMEM=y for years now. It
is probably time to flip this default for x86 and arm64.

Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Laura Abbott <labbott@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: kernel-hardening@lists.openwall.com
Link: http://lkml.kernel.org/r/20171201201000.GA44539@beast
Signed-off-by: Ingo Molnar <mingo@kernel.org>

lib/Kconfig.debug

@@ -1985,7 +1985,7 @@ config STRICT_DEVMEM
 	bool "Filter access to /dev/mem"
 	depends on MMU && DEVMEM
 	depends on ARCH_HAS_DEVMEM_IS_ALLOWED
-	default y if TILE || PPC
+	default y if TILE || PPC || X86 || ARM64
 	---help---
 	  If this option is disabled, you allow userspace (root) access to all
 	  of memory, including kernel and userspace memory. Accidental