arm64: remove redundant FRAME_POINTER kconfig option and force to select it

FRAME_POINTER is defined in lib/Kconfig.debug, it is unnecessary to redefine it
in arch/arm64/Kconfig.debug.

ARM64 depends on frame pointer to get correct stack trace (also selecting
ARCH_WANT_FRAME_POINTERS). However, the lib/Kconfig.debug definition allows
such option to be disabled. This patch forces FRAME_POINTER always on on arm64.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -27,6 +27,7 @@ config ARM64
 	select CPU_PM if (SUSPEND || CPU_IDLE)
 	select DCACHE_WORD_ACCESS
 	select EDAC_SUPPORT
+	select FRAME_POINTER
 	select GENERIC_ALLOCATOR
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CLOCKEVENTS_BROADCAST

arch/arm64/Kconfig.debug

@@ -2,10 +2,6 @@ menu "Kernel hacking"
 
 source "lib/Kconfig.debug"
 
-config FRAME_POINTER
-	bool
-	default y
-
 config ARM64_PTDUMP
 	bool "Export kernel pagetable layout to userspace via debugfs"
 	depends on DEBUG_KERNEL