i.MX31: Start the I2C clock on driver initialisation

i.MX31: Start the I2C clock on driver initialisation

i.MX31 powers on with most clocks running, so, after a power on this explicit
clock start up is not required. However, as Linux boots it disables most clocks
to save power. This includes the I2C clock. If we then soft reboot from Linux
the I2C clock stays off. This breaks the phycore, which has its environment in
I2C EEPROM. Fix the problem by explicitly starting the clock in I2C driver
initialisation routine.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
Ack-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>