x86: offer frame pointers in all build modes

CONFIG_FRAME_POINTERS=y results in much better debug info for the
kernel (clear and precise backtraces), with the only drawback being
a ~1% increase in kernel size.

So offer it unconditionally and enable it by default.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/Kconfig

@@ -27,6 +27,7 @@ config X86
 	select HAVE_IOREMAP_PROT
 	select HAVE_KPROBES
 	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select ARCH_WANT_FRAME_POINTERS
 	select HAVE_KRETPROBES
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_DYNAMIC_FTRACE

lib/Kconfig.debug

@@ -566,14 +566,14 @@ config DEBUG_NOTIFIERS
 config FRAME_POINTER
 	bool "Compile the kernel with frame pointers"
 	depends on DEBUG_KERNEL && \
-		(X86 || CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \
-		 AVR32 || SUPERH || BLACKFIN || MN10300)
-	default y if DEBUG_INFO && UML
+		(CRIS || M68K || M68KNOMMU || FRV || UML || S390 || \
+		 AVR32 || SUPERH || BLACKFIN || MN10300) || \
+		ARCH_WANT_FRAME_POINTERS
+	default y if (DEBUG_INFO && UML) || ARCH_WANT_FRAME_POINTERS
 	help
-	  If you say Y here the resulting kernel image will be slightly larger
-	  and slower, but it might give very useful debugging information on
-	  some architectures or if you use external debuggers.
-	  If you don't debug the kernel, you can say N.
+	  If you say Y here the resulting kernel image will be slightly
+	  larger and slower, but it gives very useful debugging information
+	  in case of kernel bugs. (precise oopses/stacktraces/warnings)
 
 config BOOT_PRINTK_DELAY
 	bool "Delay each boot printk message by N milliseconds"