ixgbe: Provide unlocked I2C methods

Most I2C accesses take and release semaphores for each access. Now
there is a reason to perform multiple I2C operations under the same
holding of the semaphore, so provide unlocked I2C methods for that
purpose.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>