arm: dts: iot2050: Optionally embed OTP programming data into image

Use external blob otpcmd.bin to replace the 0xff filled OTP programming
command block to create a firmware image that provisions the OTP on
first boot. This otpcmd.bin is generated from the customer keys using
steps described in the meta-iot2050 integration layer for the device.

Based on original patch by Baocheng Su.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>