bootimg.bbclass: fix settings for grub-efi.bbclass

Fixed:
- Found potential conflicted var LABELS ...
  Set LABELS to "boot install" would build out broken images when build
  vm + live together, use set_live_vm_vars() to fix the problem.

- Use ROOT and LABEL in boot-directdisk.bbclass and image-foo.bbclass,
  they are not only used by syslinux.bbclass, but also grub-efi.bbclass,
  add "SYSLINUX_" prefix would mislead users.

(From OE-Core rev: d7d1e0193c94abb1cd2daf1c298c8c1788f3616d)

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/syslinux.bbclass

@@ -33,23 +33,12 @@ AUTO_SYSLINUXMENU ?= "1"
 ISO_BOOTIMG = "isolinux/isolinux.bin"
 ISO_BOOTCAT = "isolinux/boot.cat"
 MKISOFS_OPTIONS = "-no-emul-boot -boot-load-size 4 -boot-info-table"
+SYSLINUX_ROOT ?= "${ROOT}"
 APPEND_prepend = " ${SYSLINUX_ROOT} "
 
 # Need UUID utility code.
 inherit fs-uuid
 
-# Some of the vars for vm and live image are conflicted, this function
-# is used for fixing the problem.
-def syslinux_set_vars(d, suffix):
-    vars = ['SYSLINUX_ROOT', 'SYSLINUX_CFG', 'LABELS', 'INITRD']
-    for var in vars:
-        var_with_suffix = var + '_' + suffix
-        if d.getVar(var, True):
-            bb.warn('Found potential conflicted var %s, please use %s rather than %s' % \
-                (var, var_with_suffix, var))
-        elif d.getVar(var_with_suffix, True):
-            d.setVar(var, d.getVar(var_with_suffix, True))
-
 syslinux_populate() {
 	DEST=$1
 	BOOTDIR=$2