arm: Remove sksimx6 board

This board has not been converted to CONFIG_DM_MMC by the deadline.
Remove it.

Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Stefano Babic <sbabic@denx.de>
7 files changed