Use partition type 0xeb ("EtherBoot"), to avoid any attempts to mount

the Etherboot partition.

src/arch/i386/prefix/usbdisk.S

@@ -12,7 +12,7 @@
 	.space 16
 	.space 16
 	.byte 0x80, 0x01, 0x01, 0x00
-	.byte 0x01, 0x3f, 0x20, 0x01
+	.byte 0xeb, 0x3f, 0x20, 0x01
 	.long 0x00000020
 	.long 0x00000fe0