board/common: hide /var option when booting disk image

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

board/common/qemu/Config.in.in

@@ -106,6 +106,8 @@ config QEMU_DTB_EXTEND
 	depends on QEMU_LOADER_UBOOT
 	default y if QEMU_aarch64
 
+if QEMU_ROOTFS_INITRD
+
 config QEMU_RW
 	string "Writable /cfg layer"
 	depends on QEMU_ROOTFS_INITRD
@@ -123,6 +125,8 @@ config QEMU_RW_VAR
 	default "var.ext4"
 endif
 
+endif
+
 config QEMU_VPD
 	bool "Emulate a Vital Product Data (VPD) Memory"