libfdt: Fix FDT_ERR_NOTFOUND typos in documentation

The actual error is FDT_ERR_NOTFOUND, not FDT_ERR_NOT_FOUND.

Fixes: d29126c90a ("libfdt: Add iterator over properties")
Fixes: 902d0f0953 ("libfdt: Add a subnodes iterator macro")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

libfdt/libfdt.h

@@ -227,7 +227,7 @@ int fdt_next_subnode(const void *fdt, int offset);
  *		...
  *	}
  *
- *	if ((node < 0) && (node != -FDT_ERR_NOT_FOUND)) {
+ *	if ((node < 0) && (node != -FDT_ERR_NOTFOUND)) {
  *		Error handling
  *	}
  *
@@ -566,7 +566,7 @@ int fdt_next_property_offset(const void *fdt, int offset);
  *		...
  *	}
  *
- *	if ((property < 0) && (property != -FDT_ERR_NOT_FOUND)) {
+ *	if ((property < 0) && (property != -FDT_ERR_NOTFOUND)) {
  *		Error handling
  *	}
  *