davinci: Remove unused i2c eeprom_read/write routines

The dm644x and dm646x board files have i2c eeprom read and
write routines but they are not used so remove them.

Signed-off-by: Mark A. Greer <mgreer@mvista.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>