[util] Fix uninitialised-variable warning in einfo.c

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/einfo.c

 				 ( ( ( char * ) einfo ) + einfo->desc ) );
 		}
 
+		/* Unmap file */
+		munmap ( start, len );
 	}
 
-	/* Unmap and close file */
-	munmap ( start, len );
+	/* Close file */
 	close ( fd );
 }