arm64: dts: rockchip: fix USB regulator on ROCK64

Currently the ROCK64 device tree specifies two regulators, vcc_host_5v
and vcc_host1_5v for USB VBUS on the device. Both of those are however
specified with RK_PA2 as the GPIO enabling them, causing the following
error when booting:

  rockchip-pinctrl pinctrl: pin gpio0-2 already requested by vcc-host-5v-regulator; cannot claim for vcc-host1-5v-regulator
  rockchip-pinctrl pinctrl: pin-2 (vcc-host1-5v-regulator) status -22
  rockchip-pinctrl pinctrl: could not request pin 2 (gpio0-2) from group usb20-host-drv  on device rockchip-pinctrl
  reg-fixed-voltage vcc-host1-5v-regulator: Error applying setting, reverse things back

Looking at the schematic, there are in fact three USB regulators,
vcc_host_5v, vcc_host1_5v and vcc_otg_v5. But the enable signal for all
three is driven by Q2604 which is in turn driven by GPIO_A2/PA2.

Since these three regulators are not controllable separately, I removed
the second one which was causing the error and added labels for all
rails to the single regulator.

Signed-off-by: Lorenz Brun <lorenz@brun.one>
Tested-by: Diederik de Haas <didi.debian@cknow.org>
Link: https://lore.kernel.org/r/20230421213841.3079632-1-lorenz@brun.one
Signed-off-by: Heiko Stuebner <heiko@sntech.de>