x86: define ARCH_WANT_FRAME_POINTERS

Commit da4276b8 changed a dependency
for FRAME_POINTER from X86 to ARCH_WANT_FRAME_POINTERS, but didn't
actually define it.

This patch adds the definition for ARCH_WANT_FRAME_POINTERS. Without it,
FRAME_POINTER can't be enabled on x86.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

lib/Kconfig.debug

@@ -570,6 +570,15 @@ config DEBUG_NOTIFIERS
 	  This is a relatively cheap check but if you care about maximum
 	  performance, say N.
 
+#
+# Select this config option from the architecture Kconfig, if it
+# it is preferred to always offer frame pointers as a config
+# option on the architecture (regardless of KERNEL_DEBUG):
+#
+config ARCH_WANT_FRAME_POINTERS
+	bool
+	help
+
 config FRAME_POINTER
 	bool "Compile the kernel with frame pointers"
 	depends on DEBUG_KERNEL && \