board: rockchip: rk3399: Remove unused board_early_init_f functions

These functions is excluded from SPL build and BOARD_EARLY_INIT_F is not
enabled for any of the affected boards, so this legacy code is not used.

Rockchip common board code already enable all regulators flagged as
always-on or boot-on in device tree, and fixed/gpio regulators now have
basic reference counting support so the original intent of this code is
no longer valid.

Remove the unneeded and unused code that used to enable usb regulators.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>