arm: Remove nsa310s board

These boards have not been converted to CONFIG_DM_USB by the deadline
and is also missing conversion to CONFIG_DM.  Remove it

Cc: Gerald Kerma <dreagle@doukki.net>
Cc: Tony Dinh <mibodhi@gmail.com>
Cc: Luka Perkov <luka.perkov@sartura.hr>
Signed-off-by: Tom Rini <trini@konsulko.com>