arm: mvebu: turris_omnia: don't guard by CONFIG_SPL_BUILD macro

We do not need to guard code in board_init() and board_late_init()
functions with the CONFIG_SPL_BUILD macro, since these functions are not
called in SPL.

Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>