ppc/85xx: Fix crashes due to generation of SPE instruction

U-Boot crashed on the last instruction:

int parse_stream_outer(struct in_str *inp, int flag)
{
effa4784:       94 21 ff 38     stwu    r1,-200(r1)
effa4788:       7c 08 02 a6     mflr    r0
effa478c:       42 9f 00 05     bcl-    20,4*cr7+so,effa4790 <parse_stream_outer+0xc>
effa4790:       7d 80 00 26     mfcr    r12
effa4794:       13 c1 b3 21     evstdd  r30,176(r1)

...which is a  SPE instruction, although -mno-spe was used.

tmp/cross/ppce500v2/bin/powerpc-angstrom-linux-gnuspe-gcc --version
powerpc-angstrom-linux-gnuspe-gcc (GCC) 4.3.3

Seems to be a known issue (since 2008-04?!)

Googled some, turns out this patch/workaround works for me on MPC8536DS.

See http://gcc.gnu.org/ml/gcc-patches/2008-04/msg00311.html for more info

Signed-off-by: Leon Woestenberg <leon@sidebranch.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

cpu/mpc85xx/config.mk

@@ -24,6 +24,11 @@
 PLATFORM_RELFLAGS += -fPIC -ffixed-r14 -meabi
 
 PLATFORM_CPPFLAGS += -ffixed-r2 -Wa,-me500 -msoft-float -mno-string
+
+# -mspe=yes is needed to have -mno-spe accepted by a buggy GCC;
+# see "[PATCH,rs6000] make -mno-spe work as expected" on
+# http://gcc.gnu.org/ml/gcc-patches/2008-04/msg00311.html
+PLATFORM_CPPFLAGS +=$(call cc-option,-mspe=yes)
 PLATFORM_CPPFLAGS +=$(call cc-option,-mno-spe)
 
 # Use default linker script.  Board port can override in board/*/config.mk