mxssb: Swap whole IVT header

While the BootROM doesn't check the IVT header, the first and last
byte were swapped, so fix this.
Signed-off-by: Marek Vasut <marex@denx.de>

mxssb.h

@@ -98,9 +98,9 @@ static inline uint32_t sb_hab_ivt_header(void)
 {
 	uint32_t ret = 0;
 	ret |= SB_HAB_IVT_TAG << 24;
-	ret |= (uint32_t)htons(sizeof(struct sb_ivt_header)) << 16;
+	ret |= sizeof(struct sb_ivt_header) << 16;
 	ret |= SB_HAB_VERSION;
-	return ret;
+	return htonl(ret);
 }
 
 struct sb_sections_header {