staging: board: Remove macro board_staging

Macro is not supposed to have flow control in it's
statement, remove.

Signed-off-by: Song Chen <chensong_2000@189.cn>
Link: https://lore.kernel.org/r/1608890085-1267-1-git-send-email-chensong_2000@189.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>