of: Move OF flags to be visible even when !CONFIG_OF

We need those to be visible even when compiling with CONFIG_OF
disabled, since even the empty of_node_*_flag() method use the
flag.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Rob Herring <robh@kernel.org>