Add latest versions of Arch

src/archlinux.ipxe

@@ -11,9 +11,9 @@ clear arch_version
 menu ${os} - ${arch} - Image Sig Checks: [${img_sigs_enabled}]
 menu Arch Linux
 item --gap Latest Releases
+item 2018.03.01 2018.03.01
 item 2018.02.01 2018.02.01
 item 2018.01.01 2018.01.01
-item 2017.12.01 2017.12.01
 choose arch_version || goto archlinux_exit
 goto boot