arm: Remove edb9315a board

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

This is also the last PL010_SERIAL using board, so remove those
references.

Cc: Sergey Kostanbaev <sergey.kostanbaev@fairwaves.ru>
Signed-off-by: Tom Rini <trini@konsulko.com>