stm32mp1: use OTP to configure MAC address and serial number

Use OTP57 and 58 for MAC address
- OTP57 = MAC address  bits [31:0]
- OTP58 = MAC address  bit  [47:32] stored in OTP  LSB's

Use manufacture information in OTP13 to OTP15 to build unique
chip id saved in env variable "serial#"
(used for USB device enumeration)

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>