Place the x86_64 boot before i686

This is a very minor change, but let's most people just press enter on bootup.
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>

configs/releng/syslinux.dual/archiso_pxe_both_inc.cfg

 INCLUDE boot/syslinux/archiso_head.cfg
-INCLUDE boot/syslinux/archiso_pxe32.cfg
 INCLUDE boot/syslinux/archiso_pxe64.cfg
+INCLUDE boot/syslinux/archiso_pxe32.cfg
 INCLUDE boot/syslinux/archiso_tail.cfg

configs/releng/syslinux.dual/archiso_sys_both_inc.cfg

 INCLUDE boot/syslinux/archiso_head.cfg
-INCLUDE boot/syslinux/archiso_sys32.cfg
 INCLUDE boot/syslinux/archiso_sys64.cfg
+INCLUDE boot/syslinux/archiso_sys32.cfg
 INCLUDE boot/syslinux/archiso_tail.cfg