davinci: da850evm: fix empty boot method list in the SPL

The list of available boot method is not part of the binary which
prevent the SPL from booting u-boot or Linux.

Add the missing .u_boot_list* sections to the binary to fix it.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Reviewed-by: Tom Rini <trini@konsulko.com>