ARM: BeagleBoard-x15: Enable i2c5 clocks

On AM57xx evm I2C5 is used to detect the LCD board by reading the
EEPROM present on the bus.
Enable i2c5 clocks to help that.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>