disk: fix ESP and BIOS partition type IDs for dos

The correct partition type ID for ESP is 'ef' (not 'ef00') [1].

BIOS boot partitions aren't meant for (or required) on dos partition
tables [2].  We will eventually make this a partitionless gap in the PT,
but for now let's simply use the code for 'empty'.

[1] https://tldp.org/HOWTO/Partition-Mass-Storage-Definitions-Naming-HOWTO/x190.html
[2] https://www.gnu.org/software/grub/manual/grub/html_node/BIOS-installation.html#BIOS-installation

pkg/disk/disk.go

@@ -67,11 +67,14 @@ const (
 	// Partition type ID for any native Linux filesystem on dos
 	DosLinuxTypeID = "83"
 
-	// Partition type ID for BIOS boot partition on dos
-	DosBIOSBootID = "ef02"
+	// Partition type ID for BIOS boot partition on dos.
+	// Type ID is for 'empty'.
+	// TODO: drop this completely when we convert the bios BOOT space to a
+	// partitionless gap/offset.
+	DosBIOSBootID = "00"
 
 	// Partition type ID for ESP on dos
-	DosESPID = "ef00"
+	DosESPID = "ef"
 
 	// Partition type ID for swap
 	DosSwapID = "82"