dtc: libfdt: Introduce a can_assume check in fdt_check_full

The current upstream method of having a function omit various tests is
to use the can_assume macro. Take the logic we had previously been using
and instead make it a can_assume(PERFECT) check within fdt_check_full
itself.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>

scripts/dtc/libfdt/fdt_check.c

@@ -21,6 +21,8 @@ int fdt_check_full(const void *fdt, size_t bufsize)
 	const char *propname;
 	bool expect_end = false;
 
+	if (can_assume(PERFECT))
+		return 0;
 	if (bufsize < FDT_V1_SIZE)
 		return -FDT_ERR_TRUNCATED;
 	if (bufsize < fdt_header_size(fdt))