toradex: common: Improve product/serial print during boot

Add product id print in show_board_info(), with an increasing number of
Toradex SKUs available with small differences it makes sense to print it.

Move serial number print to a dedicated line, this prevents the previous
line with the product name to overflow the 80 columns with any
reasonable product name length.

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>