up_down_mixer: hifi3: 8-byte align downmix coefficient array

downmix16bit_4ch_mono() loads its coeffs[] array with AE_L16X4_X, an
aligned 64-bit HiFi load that requires 8-byte alignment. The uint16_t
stack array is only 2-byte aligned, so the compiler may place it on a
4-byte boundary and trigger a misaligned access. Force 8-byte alignment
to match the intrinsic's requirement.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

src/audio/up_down_mixer/up_down_mixer_hifi3.c

@@ -1247,7 +1247,7 @@ void downmix16bit_4ch_mono(struct up_down_mixer_data *cd, const uint8_t * const
 	uint32_t idx3 = get_channel_index(cd->in_channel_map, 2);
 	uint32_t idx4 = get_channel_index(cd->in_channel_map, 3);
 
-	uint16_t coeffs[4] = {cd->downmix_coefficients[idx1],
+	uint16_t coeffs[4] __attribute__((aligned(8))) = {cd->downmix_coefficients[idx1],
 			      cd->downmix_coefficients[idx2],
 			      cd->downmix_coefficients[idx3],
 			      cd->downmix_coefficients[idx4]