sh: fix kconfig unmet dependency warning for FRAME_POINTER

FRAME_POINTER depends on DEBUG_KERNEL so DWARF_UNWINDER should
depend on DEBUG_KERNEL before selecting FRAME_POINTER.

WARNING: unmet direct dependencies detected for FRAME_POINTER
  Depends on [n]: DEBUG_KERNEL [=n] && (M68K || UML || SUPERH [=y]) || ARCH_WANT_FRAME_POINTERS [=n]
  Selected by [y]:
  - DWARF_UNWINDER [=y]

Fixes: bd353861 ("sh: dwarf unwinder support.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Matt Fleming <matt@console-pimps.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Tested-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Rich Felker <dalias@libc.org>

arch/sh/Kconfig.debug

@@ -54,6 +54,7 @@ config DUMP_CODE
 
 config DWARF_UNWINDER
 	bool "Enable the DWARF unwinder for stacktraces"
+	depends on DEBUG_KERNEL
 	select FRAME_POINTER
 	default n
 	help