rockchip: rk3399: use regulators_enable_boot_on() to init regulator

Use regulators_enable_boot_on() instead of init regulators one by one,
the interface can init all the regulators with regulator-boot-on property.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>