bootimg.bbclass: only inherit syslinux when pcbios

syslinux.bbclass should not be seen when use efi.

(From OE-Core rev: f994eef0aeae861857756d3cc05c49cca17bd12b)

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

@@ -20,7 +20,7 @@
 do_bootimg[depends] += "${MLPREFIX}syslinux:do_populate_sysroot \
                         syslinux-native:do_populate_sysroot"
 
-ISOLINUXDIR = "/isolinux"
+ISOLINUXDIR ?= "/isolinux"
 SYSLINUXDIR = "/"
 # The kernel has an internal default console, which you can override with
 # a console=...some_tty...
@@ -30,10 +30,9 @@ SYSLINUX_SERIAL_TTY ?= "console=ttyS0,115200"
 SYSLINUX_PROMPT ?= "0"
 SYSLINUX_TIMEOUT ?= "50"
 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 ?= "${ROOT}"
+SYSLINUX_CFG_VM  ?= "${S}/syslinux_vm.cfg"
+SYSLINUX_CFG_LIVE ?= "${S}/syslinux_live.cfg"
 APPEND_prepend = " ${SYSLINUX_ROOT} "
 
 # Need UUID utility code.