rockchip: rk3308: Remove OTP device node from soc u-boot dtsi

rockchip: rk3308: Remove OTP device node from soc u-boot dtsi

The merged upstream DT node for OTP differs in nodename and will cause
following build errors once rk3308.dtsi in dts/upstream is updated:

  ERROR (duplicate_label): /nvmem@ff210000: Duplicate label 'otp' on /nvmem@ff210000 and /efuse@ff210000
  ERROR (duplicate_label): /nvmem@ff210000/id@7: Duplicate label 'cpu_id' on /nvmem@ff210000/id@7 and /efuse@ff210000/id@7

Remove the OTP device node from soc u-boot dtsi in preparation for
replacing it with the merged upstream DT node in dts/upstream.

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