fix include order and unify local include placement

In commit https://github.com/linux-can/can-utils/commit/b153fe3f3591
("clang-tidy: sort includes alphabetically") the position of the "lib.h"
include has been moved in a way that struct canfd_frame has not been
defined anymore and lead to a warning when compiling cangen.c

This patch reverts that specific move and unifies the location of local
includes at the end of the include list.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>

j1939cat.c

@@ -21,6 +21,7 @@
 #include <linux/socket.h>
 
 #include "libj1939.h"
+
 #define J1939_MAX_ETP_PACKET_SIZE (7 * 0x00ffffff)
 #define JCAT_BUF_SIZE (1000 * 1024)