[media] mtk-vcodec: fix sparse warning

This patch fix sparse warning when running with parameters:
C=2 CF="-D__CHECK_ENDIAN__"

Signed-off-by: Tiffany Lin <tiffany.lin@mediatek.com>
Signed-off-by: PoChun Lin <pochun.lin@mediatek.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/mtk-vcodec/venc/venc_vp8_if.c

@@ -252,13 +252,18 @@ static int vp8_enc_compose_one_frame(struct venc_vp8_inst *inst,
 	u32 bs_hdr_len;
 	unsigned int ac_tag_size;
 	u8 ac_tag[MAX_AC_TAG_SIZE];
+	u32 tag;
 
 	bs_frm_size = vp8_enc_read_reg(inst, VENC_BITSTREAM_FRAME_SIZE);
 	bs_hdr_len = vp8_enc_read_reg(inst, VENC_BITSTREAM_HEADER_LEN);
 
 	/* if a frame is key frame, not_key is 0 */
 	not_key = !inst->vpu_inst.is_key_frm;
-	*(u32 *)ac_tag = __cpu_to_le32((bs_hdr_len << 5) | 0x10 | not_key);
+	tag = (bs_hdr_len << 5) | 0x10 | not_key;
+	ac_tag[0] = tag & 0xff;
+	ac_tag[1] = (tag >> 8) & 0xff;
+	ac_tag[2] = (tag >> 16) & 0xff;
+
 	/* key frame */
 	if (not_key == 0) {
 		ac_tag_size = MAX_AC_TAG_SIZE;