Cleanup CONFIG_VERSION_VARIABLE migration

CONFIG_VERSION_VARIABLE had already been mostly migrated to Kconfig,
but two headers still referenced it. Also set defaults so that
most of the defconfigs inherit the default rather than needing it
to be set explicitly.

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Petr Vorel <petr.vorel@gmail.com>
diff --git a/configs/apalis_imx6_nospl_com_defconfig b/configs/apalis_imx6_nospl_com_defconfig
index 976a66e..89af27f 100644
--- a/configs/apalis_imx6_nospl_com_defconfig
+++ b/configs/apalis_imx6_nospl_com_defconfig
@@ -9,6 +9,7 @@
 CONFIG_BOOTDELAY=1
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SUPPORT_RAW_INITRD=y
+CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_BOARD_EARLY_INIT_F=y