kmemcheck: make kconfig accessible for other architectures

The Kconfig options of kmemcheck are hidden under arch/x86 which makes porting
to other architectures harder. To fix that, move the Kconfig bits to
lib/Kconfig.kmemcheck and introduce a CONFIG_HAVE_ARCH_KMEMCHECK config option
that architectures can define.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 68f5578..711b214 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -46,6 +46,7 @@
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZMA
+	select HAVE_ARCH_KMEMCHECK
 
 config OUTPUT_FORMAT
 	string