fsl: p1_p2_rdb: Move vsc7835 firmware uploading to board_early_init_r()

Move vsc7835 firmware uploading to board_early_init_r(), so that
the switch also can work in DM eTSEC driver.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>