I2C: the i2c controller is expected to be enabled when there is a

I2C: the i2c controller is expected to be enabled when there is a
transfer request. Runtiem resume should only power on and initialize
the device to a known default state. Enabling the device on runtime
resume would trigger a spurious interrupt even when there is no
function driver acutally using the i2c device, thus causing a kernel
panic as dev->msgs == NULL.

Change-Id: I708e0d532aa0cdd7cb5161d8643dd5186d193243
Signed-off-by: Fei Yang <fei.yang@intel.com>
Reviewed-on: http://android.intel.com:8080/23503
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Tested-by: Gross, Mark <mark.gross@intel.com>