Fix discarded const qualifiers

It's unsafe to implicitly discard the const qualifier on a pointer. In
overlay_fixup_phandle(), this was probably just an oversight, and making
the "sep" variable a const char * is sufficient to fix it.

In create_node(), however, the "p" variable is directly modifying the
buffer pointed to by "const char* node_name". To fix this, we need to
actually make a duplicate of the buffer and operate on that instead.

This introduces a malloc()/free()  and an unbounded strdup() into the
operation, but fdtput isn't a long-running service and the node_name
argument comes directly from argv, so this shouldn't introduce a
significant performance impact.

Signed-off-by: Stephen Gallagher <sgallagh@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/fdt_overlay.c

@@ -407,7 +407,8 @@ static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
 		const char *fixup_str = value;
 		uint32_t path_len, name_len;
 		uint32_t fixup_len;
-		char *sep, *endptr;
+		const char *sep;
+		char *endptr;
 		int poffset, ret;
 
 		fixup_end = memchr(value, '\0', len);