dgnc: Remove unneeded dgnc_state array of strings

Dgnc_state array of strings is never used anywhere and it seems pretty
useless anyway since the board state enum names speak for themselves.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>