arm: Remove db-88f6281-bp board

This board has not been converted to CONFIG_DM_MMC by the deadline of
v2019.04, which is almost two years ago.  In addition there are other DM
migrations it is also missing.  Remove it.

Cc: Chris Packham <judge.packham@gmail.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Chris Packham <judge.packham@gmail.com>
14 files changed