arm: mvebu: turris_{omnia, mox}: Don't print model two times

arm: mvebu: turris_{omnia, mox}: Don't print model two times

Since commit 8cd4bf7dc9ba ("turris: Use checkboard() instead of
show_board_info()") the model is show two times during boot:
  Model: Turris Omnia
  Model: Turris Omnia

This is because the common function show_board_info() shows it, and
Turris' checkboard() also does.

Remove the second print.

Fixes: 8cd4bf7dc9ba ("turris: Use checkboard() instead of show_board_info()")
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>