powerpc/boot: Explicitly disable usage of SPE instructions

powerpc/boot: Explicitly disable usage of SPE instructions

commit 110a58b9f91c66f743c01a2c217243d94c899c23 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>