mn10300: Remove redundant debugging info flag

The generic makefile now sets '-Wa,--gdwarf2' in KBUILD_AFLAGS, so
this setting is no longer needed in arch makefiles.

Also remove a commented out addition of a -O1 to KBUILD_CFLAGS, and
comment text relating to these removed lines.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Geoff Levand <geoff@infradead.org> for Huawei, Linaro
Signed-off-by: Michal Marek <mmarek@suse.cz>

arch/mn10300/Makefile

@@ -92,14 +92,6 @@ define archhelp
   echo  '* zImage        - Compressed kernel image (arch/$(ARCH)/boot/zImage)'
 endef
 
-# If you make sure the .S files get compiled with debug info,
-# uncomment the following to disable optimisations
-# that are unhelpful whilst debugging.
-ifdef CONFIG_DEBUG_INFO
-#KBUILD_CFLAGS	+= -O1
-KBUILD_AFLAGS	+= -Wa,--gdwarf2
-endif
-
 #
 # include the appropriate processor- and unit-specific headers
 #