mx7ulp: add getting a board serial number

Get Unique ID of SoC iMX7ULP, using the logic described in Fusemap
(IMX7ULPRMB2_Rev0_Fusemap) attached in the i.MX 7ULP APRM [1].

[1]
https://www.nxp.com/docs/en/reference-manual/IMX7ULPRMB2.pdf



Signed-off-by: Ricardo Salveti <ricardo@foundries.io>
Co-developed-by: Oleksandr Suvorov <oleksandr.suvorov@foundries.io>
Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@foundries.io>
Reviewed-by: Fabio Estevam <festevam@gmail.com>