cmd: add tlv_eeprom command

Add support for read/write of ONIE "Tlvinfo" EEPROM data format. TLV
stands for Type-Length-Value. The data format is described here:

  https://opencomputeproject.github.io/onie/design-spec/hw_requirements.html#board-eeprom-information-format

Based on U-Boot patch from the Open Compute project:

  https://github.com/opencomputeproject/onie/blob/ec87e872d46b9805565d2c6124b2f701ef1c07b1/patches/u-boot/common/feature-sys-eeprom-tlv-common.patch



Keep only I2C EEPROM support. Use the generic eeprom driver. Fix
checkpatch issues.

Add support for multiple EEPROM TLV stores on the same system. This is
useful in case of SOM and carrier that both provide ID and hardware
configuration information.

Add option to enable for SPL. This allows selection of RAM configuration
based on EEPROM stored board identification.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>