Only extract boot/kernel partition if required

Skip getting the boot/kernel partition if it won't be installed, as
indicated in the install options. This makes it possible to use the
recovery zip installation method even on devices where parsing the
boot/kernel partition fails, by building a 'no-kernel' recovery zip.

pmos_install_functions

@@ -66,20 +66,23 @@ extract_partition_table() {
 		echo "Couldn't find $INSTALL_PARTITION partition."
 		return 1
 	fi
-	if [ "$ISOREC" = "true" ]; then
-		export KERNEL_PARTITION
-		KERNEL_PARTITION=$(findfs PARTLABEL="$KERNEL_PARTLABEL")
-		export INITFS_PARTITION
-		INITFS_PARTITION=$(findfs PARTLABEL="$INITFS_PARTLABEL")
-	else
-		dev=$(findfs PARTLABEL="boot") || \
-			dev=$(readlink -fn "$(get_fstab_device "$fstab_recovery" boot)")
-		if [ -n "$dev" ]; then
-			echo "boot partition found at $dev"
-			export BOOT_PARTITION=$dev
+
+	if [ "$FLASH_KERNEL" = "true" ]; then
+		if [ "$ISOREC" = "true" ]; then
+			export KERNEL_PARTITION
+			KERNEL_PARTITION=$(findfs PARTLABEL="$KERNEL_PARTLABEL")
+			export INITFS_PARTITION
+			INITFS_PARTITION=$(findfs PARTLABEL="$INITFS_PARTLABEL")
 		else
-			echo "Couldn't find boot partition."
-			return 1
+			dev=$(findfs PARTLABEL="boot") || \
+				dev=$(readlink -fn "$(get_fstab_device "$fstab_recovery" boot)")
+			if [ -n "$dev" ]; then
+				echo "boot partition found at $dev"
+				export BOOT_PARTITION=$dev
+			else
+				echo "Couldn't find boot partition."
+				return 1
+			fi
 		fi
 	fi
 }