use keyformat for -x509toreq, don't hard code PEM

apps/x509.c

diff --git a/apps/x509.c b/apps/x509.c
index e402f6a..3863ab9 100644
--- a/apps/x509.c
+++ b/apps/x509.c
@@ -999,7 +999,7 @@
 				else
 					{
 					pk=load_key(bio_err,
-						keyfile, FORMAT_PEM, 0,
+						keyfile, keyformat, 0,
 						passin, e, "request key");
 					if (pk == NULL) goto end;
 					}