IB/hfi1: Guard against concurrent I2C access across all chains

The discrete ASIC board design makes the two I2C chains not
independent of each other.  That is, only one chain can safely
be accessed at a time.  For discrete ASIC devices, adjust the
resource locking so that access to one I2C chain will lock both
of the chains.

Reviewed-by: Easwar Hariharan <easwar.hariharan@intel.com>
Signed-off-by: Dean Luick <dean.luick@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>