fix(xilinx): dcache flush for dtb region

flush dcache region for dtb so that dtb cache entries are first written
to disk and are invalidated afterwards to avoid presence of any stale
dtb related entry in the dcache.

Change-Id: Ide0ed58f799b35b690ed790c7498ecdc334e02f5
Signed-off-by: Amit Nagal <amit.nagal@amd.com>

plat/xilinx/common/plat_fdt.c

@@ -60,7 +60,7 @@ void prepare_dtb(void)
 		return;
 	}
 
-	clean_dcache_range((uintptr_t)dtb, fdt_blob_size(dtb));
+	flush_dcache_range((uintptr_t)dtb, fdt_blob_size(dtb));
 
 #if defined(PLAT_XLAT_TABLES_DYNAMIC)
 	ret = mmap_remove_dynamic_region((uintptr_t)dtb,