Remind reader to use correct device on EFI systems

Make sure to point out the appropriate device for EFI systems when trying to locate the UUID for the encrypted device.

Author: rmboggs

src/installation/guides/fde.md

@@ -222,7 +222,8 @@ find the UUID of the device.
 Edit the `GRUB_CMDLINE_LINUX_DEFAULT=` line in `/etc/default/grub` and add
 `rd.lvm.vg=voidvm rd.luks.uuid=<UUID>` to it. Make sure the UUID matches the one
 for the `sda1` device found in the output of the
-[blkid(8)](https://man.voidlinux.org/blkid.8) command above.
+[blkid(8)](https://man.voidlinux.org/blkid.8) command above. This will be
+`/dev/sda2` on EFI systems.
 
 ## LUKS key setup