powerpc/boot: Explicitly disable usage of SPE instructions

powerpc/boot: Explicitly disable usage of SPE instructions

commit 3cde5b89ace2d7de843ba5f505d79efca866ba7c upstream.

uImage boot wrapper should not use SPE instructions, like kernel itself.
Boot wrapper has already disabled Altivec and VSX instructions but not SPE.
Options -mno-spe and -mspe=no already set when compilation of kernel, but
not when compiling uImage wrapper yet. Fix it.

Cc: stable@vger.kernel.org
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220827134454.17365-1-pali@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>