board: gateworks: venice: enable SPL_DM_SERIAL

The uart2 and its pinmux are already marked with u-boot,dm-spl but we
need to move the call to preloader_console_init() after spl_early_init()
to avoid a board hang as dm can't be used until after spl_early_init()
due to the uart driver not enabling the uart clock.

Remove the manual config of the UART pinmux now that it is no longer
needed.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
4 files changed