ti: common: board_detect: Allow settings board detection variables manually

In some situations the EEPROM used for board detection may not be
programmed or simply programmed incorrectly. Therefore, it may be
necessary to "simulate" reading the contents of the EEPROM to set
appropriate variables used in the board detection code.

This may also be helpful in certain boot modes where doing i2c reads
may be costly and the config supports running only a specific board.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Franklin S Cooper Jr. <fcooper@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>