powerpc: Use -mtraceback=no

gcc 4.7 will be more strict about parsing the -mtraceback option:

 gcc: error: unrecognized argument in option '-mtraceback=none'
 gcc: note: valid arguments to '-mtraceback=' are: full no part

gcc used to do a 2 char compare so both "no" and "none" would
match. Switch to using -mtraceback=no should work everywhere.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Makefile

@@ -67,7 +67,7 @@ LDFLAGS_vmlinux-yy := -Bstatic
 LDFLAGS_vmlinux-$(CONFIG_PPC64)$(CONFIG_RELOCATABLE) := -pie
 LDFLAGS_vmlinux	:= $(LDFLAGS_vmlinux-yy)
 
-CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=none  -mcall-aixdesc
+CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=no -mcall-aixdesc
 CFLAGS-$(CONFIG_PPC32)	:= -ffixed-r2 -mmultiple
 KBUILD_CPPFLAGS	+= -Iarch/$(ARCH)
 KBUILD_AFLAGS	+= -Iarch/$(ARCH)